Cytology of the Liver and Spleen: Diagnostic Utility and Interpretation

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• Cytology of the liver and spleen is a minimally invasive diagnostic tool, but its utility is highly dependent on the suspected disease process and organ-specific ultrasonographic findings. For canine lymphoma staging, hepatic cytology is recommended regardless of ultrasound appearance due to low sensitivity for diffuse infiltration, while splenic cytology is reserved for ultrasonographically abnormal organs due to high negative predictive value of normal ultrasound.
• In high-risk canine mast cell tumors, ultrasonography exhibits poor sensitivity (0-29% for liver, 43-67% for spleen) for detecting visceral metastasis, necessitating routine cytologic sampling of both organs irrespective of imaging abnormalities, as cytologic evidence of metastasis significantly impacts prognosis.
• Distinguishing reactive lymphoid hyperplasia from splenic lymphoma requires careful assessment of cell morphology and population uniformity; ambiguous cases warrant referral to a clinical pathologist, and definitive diagnosis of splenic hemangiosarcoma is challenging cytologically due to poor exfoliation and frequent hemodilution, often requiring histopathology post-splenectomy.
• Sample quality is paramount, with hemodilution and blood contamination being primary limitations, particularly in the spleen; immediate smear preparation, air-drying, and Romanowsky-type staining are critical for accurate interpretation.
• Cytologic detection of visceral mast cell infiltration in dogs with high-risk mast cell tumors is a significant prognostic indicator, with evidence of metastasis correlating with significantly shorter survival times compared to dogs without such findings.
• For feline abdominal carcinomatosis, peritoneal fluid cytology alone has limited sensitivity (58%), making organ aspiration a necessary adjunct when suspicion is high, especially in cases without discrete hepatic or splenic lesions.

Fine-needle aspiration cytology of the liver and spleen is a minimally invasive, cost-effective diagnostic step in the evaluation of hepatomegaly, splenomegaly, nodular lesions, and systemic or metastatic disease. This article provides a practical framework for the collection, preparation, and interpretation of hepatic and splenic aspirates in dogs and cats, with emphasis on diagnostic reasoning and the integration of cytologic findings with ultrasonographic appearance. It is written for practicing veterinarians who perform in-house cytology or who must decide when submission to a clinical pathologist is warranted.

The central clinical question addressed here is straightforward: when does an aspirate change management, and how should the cytologic findings be weighed against imaging abnormalities? The evidence base for organ-specific sampling decisions has grown substantially, particularly in canine oncology, and this article translates those data into actionable recommendations. Histopathology is excluded from this discussion, the focus rests entirely on cytologic sampling and interpretation.

At a Glance

Physiologic and Pathologic Basis for Cytologic Sampling

The liver and spleen share several features that make them accessible to aspiration cytology. Both organs are highly cellular, moderately vascular, and diffusely involved in systemic disease processes. The hepatic parenchyma consists of cords of hepatocytes surrounding sinusoidal spaces lined by Kupffer cells and endothelial cells. The splenic parenchyma contains red pulp, dominated by erythrocytes and macrophages, and white pulp, organized as lymphoid follicles and periarteriolar lymphoid sheaths. Aspiration of either organ therefore samples a mixture of resident cell populations, circulating blood, and any infiltrative or neoplastic population present.

The diagnostic yield of an aspirate depends on whether the disease process is diffuse or nodular. Diffuse infiltrative diseases, such as lymphoma or mast cell infiltration, can often be detected by aspiration of any representative region. Nodular diseases, by contrast, require ultrasound guidance to target the lesion directly. This distinction underpins the sampling strategies recommended throughout this article.

Ultrasonographic Correlation: Strengths and Limitations

Ultrasound is the standard imaging modality used to guide hepatic and splenic aspiration, but its diagnostic performance varies markedly by disease and organ. In canine lymphoma, gray-scale ultrasonography shows a sensitivity of 72.7% and specificity of 80.6% for hepatic involvement, whereas splenic involvement is detected with 100% sensitivity but only 23.3% specificity. The practical consequence is that a normal-appearing spleen does not exclude lymphoma, and an abnormal-appearing spleen is frequently cytologically normal. For this reason, aspiration of the spleen in lymphoma staging is recommended only when the organ appears abnormal ultrasonographically, while hepatic aspiration should be performed regardless of sonographic appearance.

The opposite pattern emerges in canine mast cell tumors. Ultrasound is a poor predictor of visceral metastasis, with reported sensitivity of 43% for the spleen and 0% for the liver in one study of clinically aggressive tumors. A separate prospective study of high-risk mast cell tumors found splenic sensitivity of 67% and hepatic sensitivity of 29%, with negative predictive values of 94% and 82%, respectively. These figures indicate that a normal ultrasound does not rule out cytologic metastasis, and routine aspiration of both organs is warranted in high-risk mast cell disease regardless of imaging findings.

Sampling Technique and Sample Quality

Aspiration is performed with a 22- to 25-gauge needle attached to a 6- to 12-mL syringe. For ultrasound-guided sampling, the needle is advanced into the target organ under direct visualization, and suction is applied while the needle is moved gently within the parenchyma. Suction is released before needle withdrawal to minimize hemodilution. For splenic aspiration, a smaller needle and minimal suction reduce the risk of hemorrhage, although clinically significant bleeding after splenic aspiration is uncommon in dogs and cats with normal hemostasis.

Sample quality determines interpretive confidence. A hemodilute sample may contain too few nucleated cells to permit a definitive diagnosis, and a second aspirate should be obtained. Blood contamination is particularly problematic in the spleen, where the red pulp contributes a large erythrocyte background. Smears should be prepared immediately, air-dried, and stained with a Romanowsky-type stain. If the sample is intended for external laboratory review, submission of both stained and unstained slides is appropriate.

Cytologic Interpretation: Normal and Reactive Patterns

Normal hepatic aspirates contain cohesive clusters of hepatocytes with abundant eosinophilic cytoplasm, uniform nuclei, and occasional binucleation. Biliary epithelial cells, Kupffer cells, and mast cells appear in small numbers. The presence of numerous neutrophils, lymphocytes, or macrophages in a hepatic aspirate suggests inflammation, although peripheral blood contamination must be excluded first.

Normal splenic aspirates are dominated by small lymphocytes and erythrocytes, with variable numbers of plasma cells and macrophages. Reactive lymphoid hyperplasia produces a mixed population of small and large lymphocytes, plasma cells, and tingible-body macrophages, reflecting an antigenic stimulus. Distinguishing reactive hyperplasia from lymphoma requires attention to cell morphology and population uniformity, and cases with ambiguous features should be referred to a clinical pathologist.

Neoplastic Infiltration and Staging Implications

Cytologic detection of neoplastic infiltration in the liver or spleen carries prognostic weight in several canine malignancies. In high-risk mast cell tumors, dogs with cytologic evidence of visceral metastasis had significantly shorter survival than dogs without such evidence, with median survival of 100 versus 291 days in one study and 322 versus an unreached median in another. These findings support the inclusion of hepatic and splenic cytology in the staging of clinically aggressive mast cell tumors, even when ultrasonographic findings are unremarkable.

In lymphoma, the addition of cytology to staging protocols can shift the distribution of disease stage. One study of 186 dogs with multicentric lymphoma found that incorporating splenic and hepatic cytology moved a significant number of dogs from stage IV to stage III, a phenomenon known as stage migration. The prognostic significance of this reclassification remains uncertain, and current staging methodology in canine lymphoma may warrant revision.

Cytologic diagnosis of hemangiosarcoma is challenging because the neoplastic endothelial cells are often obscured by blood and because aspirates may yield only erythrocytes and hemosiderin-laden macrophages. A definitive cytologic diagnosis of hemangiosarcoma is therefore uncommon, and histopathology remains the diagnostic standard for this neoplasm.

Decision Framework: When to Aspirate Liver and Spleen

The decision to aspirate the liver or spleen rests on the clinical question being asked, the ultrasonographic appearance, and the suspected disease process. For lymphoma staging, the evidence supports different approaches for each organ. In dogs with confirmed lymphoma, cytologic evaluation of the liver is recommended regardless of ultrasonographic appearance, because normal hepatic ultrasound does not exclude infiltration. For the spleen, aspiration is recommended when the organ appears abnormal ultrasonographically, given that a normal splenic ultrasound carries a high negative predictive value for lymphoma in this setting Crabtree et al., diagnostic accuracy of gray-scale ultrasonography for hepatic and splenic lymphoma in dogs.

For mast cell tumor staging, the calculus reverses. Ultrasonography performs poorly at detecting early visceral metastasis. In high-risk canine mast cell tumors, ultrasound sensitivity for splenic mast cell infiltration was 43% and for hepatic infiltration was 0% in one series Book et al., correlation of ultrasound findings, liver and spleen cytology, and prognosis in high metastatic risk canine mast cell tumors. A larger prospective study confirmed that ultrasound is a poor predictor of visceral metastasis, with negative predictive values of 94% for the spleen and 82% for the liver, meaning that a normal ultrasound does not rule out metastasis Pecceu et al., ultrasound as a poor predictor of early or overt liver or spleen metastasis in high-risk mast cell tumors. Routine splenic aspiration is therefore recommended regardless of ultrasonographic appearance in dogs with clinically aggressive mast cell tumors, and hepatic aspiration should be performed even when the liver appears normal.

The staging methodology itself influences prognostic interpretation. In canine multicentric lymphoma, adding cytologic evaluation of liver and spleen shifted a significant number of dogs from stage IV to stage III, a phenomenon known as stage migration. This shift did not alter remission or survival durations in dogs receiving combination chemotherapy, which raises questions about the prognostic weight assigned to visceral cytologic findings in this disease Nerschbach et al., splenic and hepatic ultrasound and cytology in canine lymphoma. The clinician should interpret cytologic results within the staging system being used and recognize that more sensitive detection does not automatically refine prognosis.

Cytologic Pattern Guide: Liver

Hepatocellular Patterns

Normal hepatic aspirates contain cohesive sheets of hepatocytes with abundant eosinophilic cytoplasm, uniform nuclear size, and occasional binucleation. Mild anisocytosis is acceptable, particularly in older animals. Vacuolar change, either glycogen or lipid, appears as clear cytoplasmic vacuoles that may distort the nucleus. Glycogen vacuolation is finely granular and often artefactual from delayed smearing, lipid vacuolation is sharply defined and may be associated with endocrine disease, corticosteroid exposure, or metabolic disorders.

Inflammatory patterns are classified by the predominant cell type. Neutrophilic inflammation suggests cholangiohepatitis, bacterial infection, or migrating foreign material. The presence of intracellular bacteria within neutrophils supports septic cholangiohepatitis, particularly in cats. Mixed inflammation with lymphocytes and plasma cells raises the possibility of chronic hepatitis, though cytology cannot reliably grade fibrosis. Eosinophilic inflammation is uncommon and may reflect parasitic migration, eosinophilic enteritis with hepatic extension, or drug reaction.

Hepatocellular Neoplasia versus Hyperplasia

Differentiating hepatocellular adenoma from well-differentiated hepatocellular carcinoma on cytology is unreliable. Both produce sheets of hepatocytes with mild atypia. Features that favour carcinoma include marked anisocytosis, nuclear pleomorphism, prominent nucleoli, and loss of cohesiveness. Even with these features, histopathology is required for definitive classification. The cytologist should report the findings as hepatocellular neoplasia, with a comment that grade and behavior require biopsy.

Hepatic Round Cell Infiltration

Lymphoma in the liver appears as a monomorphic population of medium to large lymphoid cells with scant cytoplasm, coarse chromatin, and visible nucleoli. Small lymphocytic lymphoma can be difficult to distinguish from reactive lymphocytosis, a monotonous population of small lymphocytes with minimal variation is more consistent with neoplasia. Mast cell infiltration in the liver is identified by sheets of mast cells with metachromatic cytoplasmic granules. In dogs with high-risk mast cell tumors, cytologic detection of hepatic mast cells carries prognostic weight: dogs with cytologic evidence of visceral mast cell infiltration had significantly shorter survival than those without Book et al., correlation of ultrasound findings, liver and spleen cytology, and prognosis in high metastatic risk canine mast cell tumors. The distinction between early metastasis, defined as scattered mast cells in an otherwise normal parenchyma, and overt metastasis, defined as dense sheets or clusters, is clinically meaningful because median time to progression differs substantially between these categories Pecceu et al., ultrasound as a poor predictor of early or overt liver or spleen metastasis in high-risk mast cell tumors.

Cytologic Pattern Guide: Spleen

Normal and Reactive Splenic Cytology

The normal splenic aspirate is hemodilute and contains a mixed population of lymphocytes, plasma cells, and occasional neutrophils. Extramedullary hematopoiesis is common in dogs and appears as megakaryocytes, rubricytes, and metamyelocytes. A reactive spleen shows increased cellularity with a mixed lymphoid population, plasma cells, and tingible-body macrophages. This pattern is non-specific and may accompany inflammation, immune stimulation, or early neoplasia.

Splenic Neoplasia

Lymphoid neoplasia in the spleen presents as a monomorphic population of large lymphoid cells. The distinction between lymphoma and reactive lymphoid hyperplasia is usually straightforward when the population is large and uniform, but marginal zone lymphoma and other indolent forms can mimic reactive patterns. Histiocytic sarcoma appears as large pleomorphic cells with abundant cytoplasm, often with phagocytosed erythrocytes or leukocytes. The cells may be binucleate or multinucleate and show marked atypia.

Mast cell neoplasia in the spleen is cytologically similar to hepatic involvement. The presence of mast cells in a splenic aspirate from a dog with a cutaneous mast cell tumor confirms visceral metastasis and carries a guarded prognosis. In cats, splenic mast cell disease may be primary, and the cytologic pattern is identical regardless of origin.

Vascular Neoplasia and the Diagnostic Gap

Hemangiosarcoma is a common splenic neoplasm in dogs, but cytologic diagnosis is frequently unrewarding. The tumor is composed of vascular channels lined by neoplastic endothelial cells that exfoliate poorly. Aspirates often yield blood with few diagnostic cells. A hemorrhagic aspirate from a splenic mass should not be interpreted as benign. The diagnosis of hemangiosarcoma is typically confirmed by histopathology after splenectomy, and the clinical context, including signalment, ultrasonographic appearance, and the presence of hemoperitoneum, guides the decision to proceed to surgery De Nardi et al., diagnosis, prognosis, and treatment of canine hemangiosarcoma. Cytology is most useful for excluding other neoplasms such as lymphoma or mast cell tumor, which are cytologically diagnosable and may be treated medically instead of surgically.

Documentation and Reporting Standards

Cytologic reports should state sample quality, cellularity, and the predominant cell populations. A descriptive interpretation should be followed by a cytologic diagnosis that fits one of the following categories: non-diagnostic, normal, reactive, inflammatory, neoplastic, or suspicious for neoplasia. When neoplasia is suspected but the cell type is ambiguous, the report should list differential diagnoses in order of likelihood and recommend histopathology where the distinction changes management.

Sample quality assessment follows the ASVCP quality assurance guidelines. A sample is adequate when it contains sufficient intact parenchymal cells to assess the organ of interest. Hemodilute samples from the spleen may still be diagnostic if lymphoid or mast cell populations are present. Acellular samples from a splenic mass should be reported as non-diagnostic, with a comment that vascular neoplasia cannot be excluded.

Species and Clinical Context Modifications

Feline hepatic cytology carries a higher risk of hemorrhage than canine cytology, particularly in cats with hepatic lipidosis where the liver is friable. The spleen in cats is less commonly aspirated than in dogs, and the procedure is reserved for cases with splenomegaly or a visible mass. Feline carcinomatosis often presents with peritoneal effusion and omental or peritoneal masses instead of discrete hepatic or splenic lesions. Peritoneal fluid cytology alone detected malignant cells in only 58% of cats with confirmed carcinomatosis, so organ aspiration should be pursued when the index of suspicion is high Monteiro and O'Brien, sonographic findings of abdominal carcinomatosis in cats.

In production animals, hepatic aspiration is performed for suspected hepatic lipidosis in dairy cattle and for lymphoma in cattle and small ruminants. Splenic aspiration is uncommon in production species and is generally reserved for suspected splenic lymphoma or abscessation. The WOAH terrestrial animal health standards should be consulted when cytologic findings raise suspicion for reportable diseases, particularly in cases of unexplained hepatosplenomegaly in cattle or small ruminants.

Patient status modifies the decision to aspirate. A dog with a bleeding diathesis, severe thrombocytopenia, or prolonged clotting times is at higher risk for hemorrhage after hepatic or splenic aspiration. In these patients, the diagnostic benefit must be weighed against the risk, and alternative approaches such as ultrasound-guided biopsy or surgical sampling should be considered. The AVMA practice resources provide general guidance on procedural safety and informed consent that applies to cytologic sampling.

Recognized Complications and Early Detection

Aspiration of the liver and spleen is generally safe, but complications occur and must be recognized promptly. Hemorrhage is the most clinically significant risk, particularly with splenic aspiration in patients with thrombocytopenia, coagulopathy, or vascular neoplasia. Mild hemorrhage along the needle track is common and clinically silent. Severe hemorrhage is uncommon but can be life-threatening, especially when a splenic haemangiosarcoma is penetrated. Detect hemorrhage early by monitoring heart rate, mucous membrane color, and packed cell volume before and after sampling in high-risk patients. Ultrasonographic re-evaluation of the sampling site immediately after aspiration can identify active bleeding. Puncture of adjacent structures, including the gallbladder, stomach, or intestine, occurs when needle placement is not visualized continuously. Bile peritonitis from gallbladder penetration is rare but serious, suspect it when a patient develops abdominal pain, fever, or deteriorating perfusion within 24 to 48 hours after sampling. Pneumothorax can follow hepatic aspiration when the needle tracks cranial to the diaphragm, particularly in thin dogs or cats with a narrow thoracic inlet. Detect this complication with thoracic auscultation and, if clinical signs develop, thoracic imaging.

Common Errors and Corrective Actions

Less experienced clinicians frequently misclassify normal hepatic vacuolation as pathologic lipidosis, or interpret the hemodilute, poorly cellular splenic aspirate as a failed sample when it may represent normal red pulp. The corrective action is to assess cellularity relative to blood contamination and to evaluate the predominant cell population instead of the background. Another common error is overinterpreting mast cells in hepatic or splenic aspirates from dogs with inflammatory disease or regenerative responses. A few well-granulated mast cells can accompany chronic inflammation, the diagnosis of mast cell neoplasia requires sheets or clusters of mast cells, often with eosinophils, and ideally correlation with clinical stage. Students and new graduates often aspirate only one site per organ. In lymphoma staging, the evidence supports sampling multiple sites, since cytologic detection of lymphoma in the liver of dogs is improved by aspirating three separate sites regardless of ultrasonographic appearance Crabtree et al., diagnostic accuracy of gray-scale ultrasonography for hepatic and splenic lymphoma in dogs. A related error is trusting a normal ultrasound to exclude metastasis. In high-risk canine mast cell tumors, ultrasound sensitivity for hepatic metastasis was 0% in one series and 29% in a larger prospective study, so a normal liver on ultrasound does not rule out cytologic metastasis Book et al., correlation of ultrasound findings, liver and spleen cytology, and prognosis in high metastatic risk canine mast cell tumors, Pecceu et al., ultrasound as a poor predictor of early or overt liver or spleen metastasis in high-risk mast cell tumors.

Limitations of the Evidence and Divergent Expert Opinion

The evidence base for cytologic staging of the liver and spleen is strongest in canine lymphoma and mast cell tumors and thinner in other contexts. In canine lymphoma, adding cytology to ultrasonography shifted dogs from stage IV to stage III, but neither ultrasound nor cytology findings influenced remission duration or survival in dogs receiving combination chemotherapy Nerschbach et al., splenic and hepatic ultrasound and cytology in canine lymphoma. This raises an unresolved question: whether cytologic detection of visceral involvement carries prognostic weight or merely reflects tumor burden that other staging variables already capture. Expert opinion differs on whether routine splenic aspiration is warranted in all dogs with high-risk mast cell tumors or only when the spleen appears abnormal. The available data favour routine aspiration, since ultrasound sensitivity for splenic metastasis was 43% in one study and 67% in another, with negative predictive values of 94% in the larger series Book et al., Pecceu et al.. For splenic haemangiosarcoma, cytology has a well-recognized diagnostic gap. Aspirates are frequently hemodilute and may yield only blood, and the diagnosis often rests on histopathology after splenectomy De Nardi et al., diagnosis, prognosis, and treatment of canine hemangiosarcoma, ABROVET consensus. In feline carcinomatosis, cytology of peritoneal fluid detected malignant cells in only 58.3% of confirmed cases, so a negative fluid cytology does not exclude carcinomatosis Monteiro and O'Brien, sonographic findings of abdominal carcinomatosis in 14 cats.

Referral, Consultation, and Reporting Thresholds

Refer the patient for specialist evaluation when cytologic findings are ambiguous, when a suspected vascular neoplasm requires surgical planning, or when the aspirate is non-diagnostic and the clinical suspicion for neoplasia remains high. Consultation with a clinical pathologist is appropriate when the smear contains an unusual cell population, when round cell neoplasia cannot be subtyped cytologically, or when sample quality limits interpretation. Laboratory involvement may extend to flow cytometry, immunocytochemistry, or PCR for antigen receptor rearrangement when lymphoma is suspected but cytology is equivocal. Quality assurance standards for sample handling and reporting follow the American Society for Veterinary Clinical Pathology quality assurance and laboratory standards guidelines. Regulatory reporting is rarely triggered by cytologic findings alone, but clinicians should be aware that certain zoonotic or notifiable diseases may present with hepatic or splenic lesions, and reporting obligations vary by jurisdiction. Consult the World Organization for Animal Health terrestrial animal health standards for internationally notifiable diseases and local veterinary authorities for regional requirements. When cytology suggests an infectious agent, such as fungal organizms or Leishmania amastigotes, confirm with culture, serology, or molecular testing before initiating specific therapy.

Frequently Asked Questions

How should I proceed when ultrasound guidance is unavailable for hepatic or splenic aspiration?

Blind percutaneous aspiration is acceptable when ultrasonography is not accessible, but it carries a higher risk of sampling error and complications. Use a palpable spleen or liver margin when possible, and aspirate multiple sites to improve diagnostic yield. For the liver, approach from the right cranial abdomen, caudal to the diaphragm. For the spleen, approach from the left cranial abdomen. Apply gentle negative pressure with a 22-gauge needle attached to a 6 mL syringe, and release suction before withdrawing. If blood contaminates the sample, redirect and try again. Submit the best-quality slides even if cellularity is marginal. Document the absence of ultrasound guidance in the record, as this affects interpretation of negative results.

What is the minimum number of aspiration sites needed for reliable staging of lymphoma or mast cell tumors?

For lymphoma staging, aspirate three separate sites in the liver and three in the spleen, as described in the diagnostic accuracy study of gray-scale ultrasonography for hepatic and splenic lymphoma. For high-risk mast cell tumors, aspirate the spleen regardless of ultrasonographic appearance, since ultrasound sensitivity for splenic infiltration is only 43% in one study of ultrasound and cytology in high-risk canine mast cell tumors. The liver should also be sampled, though ultrasound sensitivity there is even lower. If the first site yields only blood or scant cells, repeat at a different location. A single aspirate from one organ is insufficient for staging decisions that alter treatment and prognosis.

How do I interpret a splenic aspirate that shows only peripheral blood?

A blood-only sample is nondiagnostic and must not be reported as normal. Redilute the sample or aspirate a different region, preferably the splenic margin or a visibly abnormal area. If repeated attempts yield only blood, consider that the lesion may be vascular, such as hemangiosarcoma, which frequently exfoliates poorly and presents a known diagnostic gap in canine hemangiosarcoma consensus guidance. In that setting, cytology cannot exclude neoplasia, and histopathology or advanced imaging should be recommended. Report the sample as nondiagnostic due to hemodilution, and document that a negative cytologic finding does not rule out vascular neoplasia. This distinction matters for client communication and for staging accuracy.

When is it appropriate to skip cytology and proceed directly to histopathology?

Proceed directly to histopathology when the lesion is a solitary mass that would be excised regardless of cytologic findings, when the patient is a surgical candidate for splenectomy or liver lobectomy, or when cytology has already been nondiagnostic and the clinical suspicion for neoplasia remains high. Cytology is most useful for diffuse infiltrative disease, staging of known systemic neoplasia, and confirmation of round cell tumors. For vascular lesions, cytology frequently fails to provide a definitive diagnosis, and the consensus review on canine hemangiosarcoma supports histopathology as the diagnostic standard. Cost and anesthetic risk also factor into this decision. If the owner declines surgery, cytology may still offer supportive information, but its limitations must be stated clearly.

How should I document cytologic findings in the medical record for staging purposes?

Record the indication for sampling, the imaging findings at each site, the number of aspirates per organ, and the sample quality. Describe the cytologic findings using standardized terminology, including cellularity, cell types present, and any evidence of infiltration. State the cytologic interpretation explicitly, such as "no evidence of neoplastic infiltration" or "round cell infiltration consistent with lymphoma." Note any discrepancy between ultrasonographic and cytologic findings, since ultrasound is a poor predictor of liver metastasis in high-risk mast cell tumors and can be falsely reassuring. Include the clinical stage assigned and how the cytology influenced that stage. This documentation supports treatment decisions, client discussions, and future comparisons if restaging is performed.

How do I explain the value and limits of cytology to an owner who declines histopathology?

Explain that cytology is a rapid, low-risk sampling method that can identify many infiltrative and round cell diseases, but it cannot always distinguish benign from malignant lesions or detect poorly exfoliating tumors. Use the example of splenic masses, where cytology may miss vascular neoplasia, and reference the diagnostic limitations acknowledged in veterinary oncology consensus documents. Clarify that a negative cytology does not guarantee the absence of disease, particularly in the liver, where ultrasound-guided sampling can miss metastatic infiltration. Offer histopathology as the more definitive option when the cytologic result would not change the treatment plan. If the owner declines histopathology, document that discussion and proceed with cytology as a palliative diagnostic step.

Related Clinical & Scientific Guides

• Peripheral Blood Smear Evaluation: A Step-by-Step Guide
• Reticulocyte Counts in Veterinary Medicine: Clinical Utility and Interpretation
• Cerebrospinal Fluid Analysis in Veterinary Neurology: Collection and Interpretation

References and Further Reading

• Diagnostic accuracy of gray-scale ultrasonography for the detection of hepatic and splenic lymphoma in dogs.. 2010.
• Splenic and hepatic ultrasound and cytology in canine lymphoma: effects of findings on stage migration and assessment of prognosis.. 2016.
• Correlation of ultrasound findings, liver and spleen cytology, and prognosis in the clinical staging of high metastatic risk canine mast cell tumors.. 2011.
• Diagnosis, Prognosis, and Treatment of Canine Hemangiosarcoma: A Review Based on a Consensus Organized by the Brazilian Association of Veterinary Oncology, ABROVET.. 2023.
• Ultrasound is a poor predictor of early or overt liver or spleen metastasis in dogs with high-risk mast cell tumors.. 2020.
• A retrospective study on the sonographic findings of abdominal carcinomatosis in 14 cats.. 2004.
• American Society for Veterinary Clinical Pathology Guidelines. American Society for Veterinary Clinical Pathology.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

Related Articles

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• Reticulocyte Counts in Veterinary Medicine: Clinical Utility and Interpretation
• Cytology of Body Cavity Effusions: Classification and Interpretation

This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.