# Cytology of the Liver and Spleen in Veterinary Patients ## Quick Answer - Perform hepatic and splenic aspiration cytology when physical examination, imaging, or blood work suggests infiltrative disease, and use the results to distinguish inflammatory, benign, and malignant processes. - Submit high-quality smears with clinical history and differential diagnoses to a clinical pathologist, and pair cytology with histopathology when a definitive tissue diagnosis is required. - Cytology cannot reliably grade tumors, determine surgical margins, or replace histologic assessment of tissue architecture, so interpret negative or equivocal results with caution. ## At a Glance | Clinical Scenario | Recommended Action | Key Cytologic Finding | Interpretation Caveat | |---|---|---|---| | Hepatomegaly with elevated liver enzymes | Ultrasound-guided fine-needle aspiration | Vacuolated hepatocytes with glycogen or lipid | Vacuolar hepatopathy may reflect metabolic disease, steroid influence, or sample artifact | | Splenomegaly with weight loss or fever | Splenic aspirate with cytologic evaluation | Monomorphic population of large lymphoid cells | Lymphoma must be distinguished from reactive lymphoid hyperplasia | | Incidental splenic nodule on imaging | Aspirate if accessible, otherwise biopsy | Mast cells with variable granulation | Mast cell tumor cytology can be low-grade, so histology is advised for grading | | Diffuse hepatic disease with coagulopathy | Avoid aspiration, pursue biopsy with platelet support | Nondiagnostic or hemodilute sample | Bleeding risk may outweigh diagnostic benefit in coagulopathic patients | ## Indications for Hepatic and Splenic Aspiration ### When to Consider Hepatic Cytology Hepatic aspiration cytology is indicated when a patient presents with hepatomegaly, elevated liver enzyme activities, or ultrasonographic evidence of diffuse or nodular hepatic disease. The procedure is most useful when the clinical question is whether the liver contains an infiltrative neoplastic process, such as lymphoma, mast cell disease, or histiocytic sarcoma, or a benign metabolic condition such as vacuolar hepatopathy. In these settings, cytology can provide a rapid, minimally invasive answer that guides the next diagnostic or therapeutic step. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) describes the liver as a common site for both primary and metastatic neoplasia, and cytology is a practical first-line tool for characterizing hepatic lesions. However, cytology samples only a small population of cells and does not preserve the tissue architecture that is necessary to distinguish diffuse disease from nodular disease or to assess fibrosis. Therefore, hepatic cytology is best used as a screening test that informs whether histopathology is needed. ### When to Splenic Cytology Splenic aspiration is indicated for splenomegaly, splenic nodules, or incidental splenic lesions detected on abdominal imaging. The spleen is a common site for mast cell tumors, lymphoma, and histiocytic proliferations, and cytology can often identify these conditions with high accuracy. In addition, splenic cytology can help differentiate benign processes such as extramedullary hematopoiesis or lymphoid hyperplasia from malignant infiltrates. The [World Small Animal Veterinary Association Global Guidelines](https://wsava.org/global-guidelines) emphasize the importance of evidence-based diagnostic approaches in companion-animal practice, and splenic cytology is a component of the diagnostic workup for splenic disease. However, the spleen is a highly vascular organ, and aspiration carries a risk of hemorrhage. The decision to aspirate a splenic lesion should be based on the patient's coagulation status, the size and location of the lesion, and the likelihood that the result will change management. ## Contraindications and Risks ### Coagulopathy and Hemorrhage Risk The most important contraindication to hepatic or splenic aspiration is a clinically significant coagulopathy. The liver is the primary source of most coagulation factors, and hepatic disease can lead to prolonged clotting times. The spleen is a highly vascular organ, and even a small laceration can cause significant hemorrhage. Before performing an aspirate, the clinician should assess the patient for petechiae, ecchymoses, or a history of bleeding, and consider a platelet count and coagulation profile if there is any concern. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) notes that coagulation testing is an important part of the diagnostic evaluation of patients with liver disease. If a coagulopathy is present, the risk of aspiration may outweigh the diagnostic benefit, and the clinician should consider alternative approaches such as ultrasound-guided biopsy with a smaller needle or deferring tissue sampling until the coagulopathy is corrected. ### Lesion Location and Accessibility Lesions that are located near large blood vessels, the gallbladder, or the bile ducts may be difficult to aspirate safely. Similarly, splenic lesions that are located near the splenic hilus or that are highly vascular may be at increased risk of hemorrhage. In these cases, the clinician should weigh the diagnostic value of the aspirate against the risk of complications and consider whether a surgical biopsy is a safer alternative. ### Patient Stability Patients that are hemodynamically unstable, have severe respiratory compromise, or are in significant pain may not tolerate the positioning required for aspiration. In these cases, the clinician should stabilize the patient first and defer the aspirate until the patient is stable enough to undergo the procedure safely. ## Aspiration Technique and Sample Preparation ### Equipment and Preparation The equipment needed for hepatic and splenic aspiration includes a sterile needle, a syringe, and glass slides. A 22-gauge needle is commonly used for aspiration, and a 6- to 12-milliliter syringe provides adequate suction. The skin over the aspiration site should be clipped and prepared aseptically, and the ultrasound probe should be covered with a sterile sleeve if ultrasound guidance is used. ### Aspiration Procedure The aspiration procedure involves inserting the needle into the lesion, applying gentle suction, and then releasing the suction before withdrawing the needle. The goal is to obtain a small amount of cellular material without excessive blood contamination. The sample is then expelled onto a glass slide and a smear is prepared using a second slide. The [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/) provides educational resources on sample preparation and cytologic evaluation. A well-prepared smear is thin, evenly distributed, and contains a sufficient number of intact cells for evaluation. The smear should be air-dried and stained with a Romanowsky-type stain such as Diff-Quik or Wright-Giemsa. ### Ultrasound Guidance Ultrasound guidance is recommended for hepatic and splenic aspiration because it allows the clinician to visualize the needle tip and to target the lesion directly. Ultrasound guidance reduces the risk of puncturing adjacent structures and increases the likelihood of obtaining a diagnostic sample. The [American Animal Hospital Association](https://www.aaha.org/resources) provides practice guidelines that emphasize the importance of diagnostic imaging in the evaluation of abdominal disease. ## Sample Quality and Preparation ### Smear Preparation The quality of the smear is the most important factor in the diagnostic yield of cytology. A good smear is thin, has a feathered edge, and contains a monolayer of cells. The smear should be prepared immediately after the aspirate is obtained, and it should be air-dried quickly to preserve cell morphology. ### Staining Romanowsky-type stains are the most commonly used for cytologic evaluation. These stains provide good nuclear and cytoplasmic detail and are suitable for most diagnostic questions. The stain should be fresh and properly prepared to avoid artifacts that can obscure the cells. ### Sample Submission When submitting a sample to a clinical pathologist, the clinician should provide a complete history, a description of the lesion, and the differential diagnoses. The pathologist uses this information to interpret the cytologic findings in the context of the patient's clinical presentation. The [World Organisation for Animal Health](https://www.woah.org/en/what-we-do/animal-health-and-welfare) emphasizes the importance of accurate diagnostic information for animal health and welfare, and a well-submitted sample is a key part of the diagnostic process. ## Common Cytologic Findings in the Liver ### Vacuolar Hepatopathy Vacuolar hepatopathy is a common finding in hepatic cytology. It is characterized by hepatocytes that contain large, clear vacuoles that displace the nucleus to the periphery. Vacuolar hepatopathy can be caused by a variety of conditions, including hyperadrenocorticism, diabetes mellitus, and the administration of glucocorticoids. It can also be an artifact of sample preparation, particularly if the smear is too thick or if the cells are damaged. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) describes vacuolar hepatopathy as a common response of the liver to a variety of insults. The presence of vacuolar hepatocytes does not confirm a specific diagnosis, and the clinician must correlate the cytologic findings with the patient's history, physical examination, and other diagnostic tests. ### Hepatic Lipidosis Hepatic lipidosis is a severe form of vacuolar hepatopathy in which the hepatocytes are filled with lipid. It is most commonly seen in cats, and it is often associated with a period of anorexia. The cytologic appearance of hepatic lipidosis is characterized by hepatocytes that are distended with large, clear vacuoles that do not stain with Romanowsky stains. The diagnosis is confirmed by the clinical presentation and the exclusion of other causes of vacuolar hepatopathy. ### Inflammation Hepatic inflammation can be seen in cytology as an increased number of inflammatory cells, including neutrophils, lymphocytes, and macrophages. The presence of inflammation may indicate a bacterial infection, a viral infection, or an immune-mediated process. The cytologic findings should be correlated with the results of a bacterial culture and sensitivity testing if an infectious cause is suspected. ### Neoplasia Hepatic neoplasia can be primary or metastatic. Primary hepatic tumors include hepatocellular carcinoma, cholangiocarcinoma, and hemangiosarcoma. Metastatic tumors can arise from a variety of primary sites, including the pancreas, the intestine, and the mammary gland. The cytologic appearance of a neoplastic process is characterized by a monomorphic population of cells with features of malignancy, such as an increased nuclear-to-cytoplasmic ratio, nuclear pleomorphism, and prominent nucleoli. The [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/) provides educational resources on the cytologic evaluation of hepatic and splenic disease. The interpretation of a neoplastic process requires experience and a careful evaluation of the cell morphology. ## Common Cytologic Findings in the Spleen ### Extramedullary Hematopoiesis Extramedullary hematopoiesis is a common finding in splenic cytology, and it is characterized by the presence of a mixture of erythroid and myeloid precursor cells. This finding is often seen in response to anemia or other conditions that stimulate the production of blood cells. The presence of extramedullary hematopoiesis does not indicate a neoplastic process, and it is usually a benign finding. ### Lymphoid Hyperplasia Lymphoid hyperplasia is a benign proliferation of lymphocytes in the spleen. It can be seen in response to an infection or an immune-mediated disease. The cytologic appearance of lymphoid hyperplasia is characterized by a mixed population of small and large lymphocytes, with a normal distribution of cell types. The presence of a monomorphic population of large lymphocytes is more concerning for lymphoma. ### Mast Cell Tumor Mast cell tumors are a common splenic neoplasm in dogs. The cytologic appearance of a mast cell tumor is characterized by a population of mast cells with a variable number of granules. The granules can be difficult to see in some cases, and the diagnosis may require special stains or histopathology. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) describes mast cell tumors as a common neoplasm in dogs, and the spleen is a common site for the disease. ### Lymphoma Lymphoma is a malignant neoplasm of lymphocytes that can affect the spleen. The cytologic appearance of lymphoma is characterized by a monomorphic population of large, immature lymphocytes. The diagnosis of lymphoma is often straightforward on cytology, but the grading of the tumor requires histopathology. ### Histiocytic Sarcoma Histiocytic sarcoma is a malignant neoplasm of histiocytes that can affect the spleen. The cytologic appearance of histiocytic sarcoma is characterized by a population of large, pleomorphic cells with a moderate amount of cytoplasm. The diagnosis of histiocytic sarcoma can be challenging on cytology, and histopathology is often required for a definitive diagnosis. ## Differentiating Benign from Malignant Processes ### Cytologic Features of Malignancy The cytologic features of malignancy include an increased nuclear-to-cytoplasmic ratio, an abnormal nuclear shape, a coarse chromatin pattern, and the presence of prominent nucleoli. The presence of these features in a monomorphic population of cells is highly suggestive of a neoplastic process. However, the absence of these features does not rule out malignancy, and the clinician should consider the possibility of a well-differentiated tumor. ### The Role of Histopathology Histopathology is the gold standard for the diagnosis of hepatic and splenic disease. Histopathology preserves the tissue architecture, which allows the pathologist to assess the relationship between the cells and the surrounding tissue. Histopathology is necessary for the grading of tumors, the assessment of surgical margins, and the differentiation of benign from malignant processes. The [American Veterinary Medical Association](https://www.avma.org/resources-tools/pet-owners) provides guidance for pet owners on the importance of a definitive diagnosis. The decision to pursue histopathology should be based on the cytologic findings, the clinical presentation, and the likelihood that the result will change the management of the patient. ### The Role of Immunocytochemistry and Flow Cytometry Immunocytochemistry and flow cytometry can be used to characterize the cell population in a cytologic sample. These techniques can be used to identify the lineage of a neoplastic cell population, such as a B-cell or T-cell lymphoma. The use of these techniques requires a specialized laboratory, and the results should be interpreted in the context of the cytologic and histopathologic findings. ## Practical Workflow for Hepatic and Splenic Aspiration ### Step 1: Clinical Assessment The first step is a thorough clinical assessment of the patient. This includes a history, a physical examination, and a review of the laboratory data. The clinician should identify the reason for the aspirate and the differential diagnoses. ### Step 2: Imaging The second step is imaging of the liver and spleen. Ultrasound is the most commonly used imaging modality, and it can be used to identify the lesion, to assess its size and location, and to guide the aspiration. The [American Animal Hospital Association](https://www.aaha.org/resources) provides guidelines for the use of diagnostic imaging in companion-animal practice. ### Step 3: Aspiration and Sample Preparation The third step is the aspiration of the lesion and the preparation of the smear. The aspiration should be performed with a technique that minimizes the risk of hemorrhage and maximizes the yield of cells. The smear should be prepared immediately and stained with a Romanowsky-type stain. ### Step 4: Cytologic Evaluation The fourth step is the cytologic evaluation of the smear. The evaluation should be performed by a clinical pathologist or a clinician with experience in cytology. The evaluation should include a description of the cell population, the presence of any abnormal cells, and the interpretation of the findings. ### Step 5: Correlation and Decision-Making The fifth step is the correlation of the cytologic findings with the clinical presentation and the decision-making. The clinician should use the cytologic findings to guide the next step, which may be a histopathologic evaluation, a therapeutic trial, or a referral to a specialist. ## Records and Measurements ### Documentation of the Procedure The clinician should document the indication for the aspirate, the technique used, the number of slides prepared, and the quality of the sample. This documentation is important for the medical record and for the interpretation of the cytologic findings. ### Cytologic Report The cytologic report should include a description of the cell population, the presence of any inflammation, and the assessment of the findings. The report should also include a differential diagnosis and a recommendation for the next step. ### Quality Control The quality of the cytologic sample is a critical determinant of the diagnostic value of the procedure. The clinician should ensure that the smear is thin, well-stained, and free of artifacts. The sample should be submitted to a clinical laboratory that has a quality-control program. ## Common Failure Patterns ### Nondiagnostic Samples A nondiagnostic sample is a common failure pattern in hepatic and splenic cytology. This can occur if the needle is not placed in the lesion, if the sample is too bloody, or if the smear is too thick. The clinician should repeat the aspirate if the sample is nondiagnostic, and the sample should be submitted to a laboratory with experience in cytology. ### Hemorrhage Hemorrhage is a potential complication of hepatic and splenic aspiration. The risk of hemorrhage is increased in patients with a coagulopathy or in patients with a lesion that is located near a blood vessel. The clinician should monitor the patient for signs of hemorrhage after the procedure. ### Misinterpretation Misinterpretation is a potential failure pattern in cytologic evaluation. The misinterpretation can occur if the sample is not representative of the lesion, if the smear is of poor quality, or if the pathologist is not experienced in cytology. The clinician should be aware of the limitations of cytology and should use histopathology when the diagnosis is uncertain. ## Limitations of Cytology ### Lack of Tissue Architecture Cytology does not preserve the tissue architecture, which is a limitation for the diagnosis of certain conditions. For example, the differentiation of a benign adenoma from a well-differentiated carcinoma may not be possible on cytology. The diagnosis of a diffuse inflammatory disease may also be difficult on cytology. ### Inability to Grade Tumors Cytology cannot be used to grade tumors. The grading of a tumor requires the assessment of the tissue architecture and the degree of invasion, which is not possible on a cytologic sample. The grading of a tumor is important for the prognosis and the treatment of the patient. ### The Need for Histopathology Histopathology is the gold standard for the diagnosis of hepatic and splenic disease. The decision to use histopathology should be made when the cytologic findings are equivocal, when the diagnosis is uncertain, or when the treatment depends on the grade of the tumor. ## Welfare and Safety Context The aspiration of the liver and spleen is a minimally invasive procedure, but it is not without risk. The clinician should consider the welfare of the patient and the safety of the procedure. The patient should be monitored for signs of pain, hemorrhage, or other complications after the procedure. The [World Organisation for Animal Health](https://www.woah.org/en/what-we-do/animal-health-and-welfare) emphasizes the importance of animal welfare in all aspects of veterinary care. The clinician should use the least invasive technique that is likely to provide a diagnosis, and the clinician should consider the welfare of the patient in the decision-making process. ## Professional Escalation Criteria The clinician should escalate the case to a specialist when the cytologic findings are equivocal, when the diagnosis is uncertain, or when the treatment depends on the grade of the tumor. The clinician should also escalate the case when the patient is unstable or when the procedure is a high risk. The [American Veterinary Medical Association](https://www.avma.org/resources-tools/pet-owners) provides guidance for pet owners on the importance of a referral to a specialist when the diagnosis is uncertain. The decision to refer the patient should be made in the best interest of the patient and the client. ## A Decision Framework for Cytology-Guided Case Management ### The Clinical Question That Drives the Procedure Every hepatic or splenic aspirate should begin with a written clinical question that the cytology result is expected to answer. This question determines whether the procedure is worth performing, which slides to prepare, and what follow-up testing is needed. A useful clinical question has three parts: the suspected disease category, the management action that will change based on the result, and the consequence of a nondiagnostic sample. For example, a clinician might ask whether a dog with splenomegaly and weight loss has lymphoma. If the cytology shows lymphoma, the next step is chemotherapy. If the cytology shows reactive lymphoid hyperplasia, the next step is monitoring and additional testing for infectious or immune-mediated disease. If the sample is nondiagnostic, the next step is histopathology. This framework prevents the common error of performing an aspirate without a plan for the result. The [American Animal Hospital Association](https://www.aaha.org/resources) practice guidelines emphasize that diagnostic testing should be selected based on how the result will change patient management. An aspirate that will not change the treatment plan is difficult to justify, especially when the patient has a bleeding risk or requires sedation. The clinician should document the clinical question in the medical record before the procedure. ### The Three-Tier Interpretation System A practical interpretation system for hepatic and splenic cytology uses three tiers. Each tier carries a distinct set of next steps and a distinct level of confidence. Tier 1 is a diagnostic result. The cytology shows a clear population of cells that answers the clinical question. Examples include a monomorphic population of large lymphocytes consistent with lymphoma, a population of mast cells consistent with mast cell neoplasia, or a mixed population of erythroid and myeloid precursors consistent with extramedullary hematopoiesis. A Tier 1 result allows the clinician to proceed with treatment or monitoring without additional tissue sampling. Tier 2 is a supportive result. The cytology shows findings that are consistent with a suspected disease but not diagnostic on their own. Examples include vacuolated hepatocytes in a patient with suspected hyperadrenocorticism or a mixed population of lymphocytes in a patient with suspected reactive hyperplasia. A Tier 2 result supports the clinical diagnosis but does not rule out a well-differentiated neoplasm. The clinician should consider histopathology when the treatment is invasive, expensive, or carries significant risk. Tier 3 is a nondiagnostic or conflicting result. The cytology shows only blood, fat, or a cell population that does not match the clinical picture. A Tier 3 result requires a repeat aspirate, a different sampling technique, or histopathology. The clinician should not use a Tier 3 result to rule out disease. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) notes that cytology is a screening tool that must be interpreted in the context of the patient's clinical presentation. The three-tier system formalizes this principle by assigning a specific action to each level of diagnostic confidence. ### The Pretest Probability Assessment The value of a cytology result depends on the pretest probability of the suspected disease. A cytology result that confirms a high-probability disease is more reliable than a result that confirms a low-probability disease. The clinician should estimate the pretest probability based on the signalment, history, physical examination, and imaging findings. For example, a young dog with a splenic mass and no other clinical signs has a lower pretest probability of lymphoma than an older dog with splenomegaly, weight loss, and hypercalcemia. A cytologic diagnosis of lymphoma in the older dog is more reliable than the same diagnosis in the young dog. The clinician should document the pretest probability in the medical record and use it to interpret the cytology result. The [World Small Animal Veterinary Association Global Guidelines](https://wsava.org/global-guidelines) emphasize the importance of evidence-based decision-making in companion-animal practice. The pretest probability assessment is a structured way to apply clinical judgment to the interpretation of a diagnostic test. It also helps the clinician decide whether histopathology is needed to confirm a cytologic diagnosis. ### The Sampling Site Selection Protocol The choice of sampling site is a decision that affects the diagnostic yield of the aspirate. The clinician should select the site based on the imaging findings and the clinical question. For a diffuse hepatic disease, the clinician should sample the liver parenchyma away from the gallbladder and large vessels. For a nodular lesion, the clinician should sample the nodule directly. The clinician should also consider the number of samples to obtain. A single aspirate may not be representative of a heterogeneous lesion. The [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/) provides educational resources on sample collection and preparation. The clinician should obtain at least two to three aspirates from different areas of the lesion to increase the diagnostic yield. For the spleen, the clinician should sample the lesion directly and avoid the splenic hilus. The hilus contains large blood vessels that increase the risk of hemorrhage. The clinician should also avoid sampling the splenic capsule, which is fibrous and may not yield a diagnostic sample. ### The Cell Population Assessment The interpretation of a cytologic sample begins with a systematic assessment of the cell population. The clinician should first determine whether the sample is cellular and whether the cells are intact. A sample with few cells or many broken cells is not diagnostic and should be repeated. The clinician should then assess the cell population in three steps. The first step is to identify the predominant cell type. The second step is to assess the distribution of cell types. The third step is to assess the cytologic features of the cells. The predominant cell type is the most common cell in the sample. In the liver, the predominant cell type is usually the hepatocyte. In the spleen, the predominant cell type is usually the lymphocyte. The distribution of cell types is the relative proportion of each cell type. A normal spleen has a mixed population of small and large lymphocytes. A monomorphic population of large lymphocytes is concerning for lymphoma. The cytologic features of the cells include the nuclear-to-cytoplasmic ratio, the nuclear shape, the chromatin pattern, and the presence of nucleoli. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) describes the cytologic features of malignancy, including an increased nuclear-to-cytoplasmic ratio, an abnormal nuclear shape, and a coarse chromatin pattern. The presence of these features in a monomorphic population of cells is highly suggestive of a neoplastic process. ### The Diagnostic Confidence Score A diagnostic confidence score is a simple tool that helps the clinician decide whether to proceed with treatment or pursue histopathology. The score is based on three factors: the quality of the sample, the clarity of the cytologic findings, and the pretest probability of the disease. The sample quality is scored as high, medium, or low. A high-quality sample is cellular, well-stained, and free of artifacts. A medium-quality sample is cellular but has some artifacts or blood contamination. A low-quality sample is not cellular or is too bloody to interpret. The clarity of the cytologic findings is scored as high, medium, or low. A high-clarity finding is a monomorphic population of cells with clear features of malignancy. A medium-clarity finding is a mixed population of cells with some atypical features. A low-clarity finding is a mixed population of cells with no atypical features. The pretest probability is scored as high, medium, or low. A high pretest probability is a clinical presentation that is strongly suggestive of the suspected disease. A medium pretest probability is a clinical presentation that is consistent with the suspected disease but not specific. A low pretest probability is a clinical presentation that is not suggestive of the suspected disease. The diagnostic confidence score is the sum of the three factors. A high score indicates that the cytology result is reliable and that the clinician can proceed with treatment. A medium score indicates that the cytology result is supportive but that histopathology is needed for a definitive diagnosis. A low score indicates that the cytology result is not reliable and that the clinician should repeat the aspirate or pursue histopathology. ### The Record System for Cytology Cases A standardized record system for cytology cases improves the quality of the medical record and the consistency of the clinical decision-making. The record should include the clinical question, the pretest probability, the sampling site, the sample quality, the cytologic findings, the diagnostic confidence score, and the next step. The record should be written in the medical record at the time of the aspirate. The clinician should document the indication for the aspirate, the technique used, the number of slides prepared, and the quality of the sample. The clinician should also document the cytologic findings and the interpretation of the findings. The [American Veterinary Medical Association](https://www.avma.org/resources-tools/pet-owners) provides guidance for pet owners on the importance of a complete medical record. A complete record allows the clinician to track the patient's progress and to make informed decisions about the next step. ### The Troubleshooting Method for Nondiagnostic Samples A nondiagnostic sample is a common failure pattern in hepatic and splenic cytology. The clinician should have a systematic method for troubleshooting a nondiagnostic sample. The first step is to assess the sample quality. A sample that is not cellular or that is too bloody is not diagnostic. The second step is to assess the sampling technique. The needle may not have been placed in the lesion, or the suction may have been too high or too low. The clinician should repeat the aspirate with a different technique. The third step is to assess the smear preparation. A smear that is too thick or too thin may not be diagnostic. The clinician should prepare a new smear with a different technique. The fourth step is to assess the staining. A smear that is overstained or understained may not be diagnostic. The clinician should restain the smear or prepare a new smear. The fifth step is to assess the clinical question. The clinical question may not be answerable by cytology. The clinician should consider histopathology or other diagnostic tests. ### The Comparison of Cytology and Histopathology The decision to use cytology or histopathology depends on the clinical question and the diagnostic confidence score. Cytology is a rapid, minimally invasive test that can provide a diagnosis in many cases. Histopathology is a more invasive test that preserves the tissue architecture and is necessary for the grading of tumors. The [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/) provides educational resources on the comparison of cytology and histopathology. The clinician should use cytology as a screening test and histopathology as a confirmatory test when the cytology result is not diagnostic or when the treatment depends on the grade of the tumor. ### The Clinical Decision-Making Workflow The clinical decision-making workflow for hepatic and splenic cytology is a step-by-step process that guides the clinician from the initial assessment to the final decision. The workflow includes the following steps: 1. Perform a thorough clinical assessment of the patient. 2. Estimate the pretest probability of the suspected disease. 3. Select the sampling site based on the imaging findings. 4. Perform the aspirate and prepare the smear. 5. Assess the sample quality and the cytologic findings. 6. Assign a diagnostic confidence score. 7. Decide whether to proceed with treatment or pursue histopathology. 8. Document the findings and the decision in the medical record. The [World Organisation for Animal Health](https://www.woah.org/en/what-we-do/animal-health-and-welfare) emphasizes the importance of a systematic approach to animal health and welfare. The clinical decision-making workflow is a systematic approach that improves the quality of the diagnostic process. ### The Role of the Clinical Pathologist The clinical pathologist plays a central role in the interpretation of cytologic samples. The pathologist provides an objective assessment of the cell population and the cytologic features. The pathologist also provides a differential diagnosis and a recommendation for the next step. The clinician should submit a complete history and a description of the lesion to the pathologist. The pathologist uses this information to interpret the cytologic findings in the context of the patient's clinical presentation. The [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/) provides resources for the submission of cytologic samples. The clinician should review the pathologist's report and discuss the findings with the pathologist if the report is unclear. The pathologist can provide additional information or recommend additional testing. ### The Clinical Decision for the Next Step The final step in the clinical decision-making workflow is the decision for the next step. The next step may be a treatment, a histopathologic evaluation, or a referral to a specialist. The decision should be based on the diagnostic confidence score and the clinical question. If the diagnostic confidence score is high, the clinician can proceed with the treatment. If the diagnostic confidence score is medium, the clinician should pursue histopathology. If the diagnostic confidence score is low, the clinician should repeat the aspirate or pursue a different diagnostic test. The [American Veterinary Medical Association](https://www.avma.org/resources-tools/pet-owners) provides guidance for pet owners on the importance of a definitive diagnosis. The clinician should use the diagnostic confidence score to guide the decision for the next step and to ensure that the patient receives the appropriate care. ## Frequently Asked Questions ### What is the difference between cytology and histopathology? Cytology is the evaluation of individual cells or small groups of cells, while histopathology is the evaluation of a tissue sample that preserves the architecture of the tissue. Histopathology is a gold standard for the diagnosis of hepatic and splenic disease, and it is used when the cytologic findings are equivocal or when the diagnosis is uncertain. ### Is a liver aspirate painful for the patient? A liver aspirate is a minimally invasive procedure that is performed with a small needle. The patient may experience some discomfort, but the procedure is generally well tolerated. The clinician should use a technique that minimizes the risk of complications and should monitor the patient for signs of pain after the procedure. ### How long does it take to get the results of a cytologic evaluation? The time to get the results of a cytologic evaluation depends on the laboratory and the complexity of the case. A preliminary result can be available within a few hours, but a final report may take a few days. The clinician should discuss the expected time with the laboratory. ### Can cytology be used to diagnose lymphoma? Cytology can be used to diagnose lymphoma, and it is often the first step in the diagnosis of the disease. The cytologic appearance of lymphoma is characterized by a monomorphic population of large cells. However, the grading of the tumor requires histopathology. ### What is the risk of hemorrhage after a splenic aspirate? The risk of hemorrhage after a splenic aspirate is low, but it is a potential complication. The risk is increased in patients with a coagulopathy or in patients with a lesion that is near a blood vessel. The clinician should monitor the patient for signs of hemorrhage after the procedure. ### Can cytology be used to diagnose mast cell tumors? Cytology can be used to diagnose mast cell tumors, and it is often the first step in the diagnosis of the disease. The cytologic appearance of a mast cell tumor is characterized by a population of mast cells with a variable number of granules. However, the grading of the tumor requires histopathology. ### What is the difference between a benign and a malignant cytologic finding? A benign cytologic finding is characterized by a mixed population of cells with a normal morphology. A malignant cytologic finding is characterized by a monomorphic population of cells with features of malignancy, such as an increased nuclear-to-cytoplasmic ratio and an abnormal nuclear shape. The presence of these features is highly suggestive of a neoplastic process. ### When should I refer a patient to a specialist? The clinician should refer a patient to a specialist when the cytologic findings are not diagnostic, when the diagnosis is uncertain, or when the treatment of the patient depends on the grade of the tumor. The clinician should also refer the patient when the patient is not a good candidate for the procedure or when the patient has a high risk of complications. ## Using the Evidence | Source | Best use in this topic | Important limitation | |---|---|---| | [Pet Care](https://www.avma.org/resources-tools/pet-owners) | official guidance | Check the linked page for current local requirements | | [AAHA Guidelines](https://www.aaha.org/resources) | official guidance | Check the linked page for current local requirements | | [Global Guidelines](https://wsava.org/global-guidelines) | official guidance | Check the linked page for current local requirements | ## Related Veterinary Guides - [Cytology of the Liver and Spleen: Diagnostic Utility and Interpretation](/knowledge/veterinary-medicine/clinical-pathology/cytology-liver-spleen-veterinary) - [Anesthesia for Patients with Gastrointestinal Disease: Aspiration Risk](/knowledge/veterinary-medicine/anesthesia-analgesia/anesthesia-patients-gastrointestinal-disease-aspiration-risk) - [Hepatomegaly in Veterinary Patients: Laboratory, Imaging, Cytology, and Biopsy Planning](/knowledge/veterinary-medicine/clinical-methods/hepatomegaly-veterinary-laboratory-imaging-cytology-biopsy-planning) - [Anesthesia for Patients with Liver Disease: Drug Metabolism and Dosing](/knowledge/veterinary-medicine/anesthesia-analgesia/anesthesia-patients-liver-disease-drug-metabolism-dosing) - [Dose Adjustment in Hepatic Disease: Pharmacokinetic Principles for Veterinary Patients](/knowledge/veterinary-medicine/clinical-pharmacology/dose-adjustment-hepatic-disease-veterinary) ## References and Further Reading - [Pet Care](https://www.avma.org/resources-tools/pet-owners). American Veterinary Medical Association. - [AAHA Guidelines](https://www.aaha.org/resources). American Animal Hospital Association. - [Global Guidelines](https://wsava.org/global-guidelines). World Small Animal Veterinary Association. - [Merck Veterinary Manual](https://www.merckvetmanual.com/). Merck Veterinary Manual. - [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/). Cornell University. - [Animal Health and Welfare](https://www.woah.org/en/what-we-do/animal-health-and-welfare). World Organisation for Animal Health. - [Correlation of ultrasound findings, liver and spleen cytology, and prognosis in the clinical staging of high metastatic risk canine mast cell tumors.](https://pubmed.ncbi.nlm.nih.gov/21689203). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2011. - [The Role of Fine Needle Aspiration of Liver and Spleen in the Staging of Low-Grade Canine Cutaneous Mast Cell Tumor.](https://pubmed.ncbi.nlm.nih.gov/36136689). Veterinary sciences, 2022. - [T-cell lymphoma involving the rectum of a dog.](https://pubmed.ncbi.nlm.nih.gov/37995445). Journal of comparative pathology, 2023. - [Acute myeloid leukemia with peripheral lymph node involvement in dogs: A retrospective study of 23 cases.](https://pubmed.ncbi.nlm.nih.gov/39540621). Veterinary pathology, 2025. - [Suspected Phenobarbital-Induced Pseudolymphoma in a Dog.](https://pubmed.ncbi.nlm.nih.gov/28865097). Journal of veterinary internal medicine, 2017. > This article is educational and is not a substitute for veterinary diagnosis or treatment. Contact a veterinarian for advice about an individual animal.