# Interpretation of Histopathology Reports: A Guide for Clinicians


## Key Takeaways

- Histopathology reports are a professional dialogue between pathologist and clinician; effective interpretation necessitates integrating tissue morphology with patient history, physical findings, and other diagnostic data, recognizing that the pathologist sees tissue but not the patient, and vice-versa.
- The morphologic diagnosis, structured by tissue, process, distribution, and severity (e.g., "Liver: moderate, diffuse, centrilobular hepatocellular vacuolation"), provides a precise lesion description that forms the foundation for clinical interpretation and differential diagnosis.
- Margin assessment in neoplastic excisions is critical for determining the need for re-excision or adjunctive therapy, with interpretation influenced by tumor type, grade, and potential for microscopic extension beyond the inked margin.
- Ancillary tests, including special stains (e.g., GMS for fungi) and immunohistochemistry, are crucial for confirming or refining morphologic diagnoses and identifying specific etiologies, but their interpretation must be contextualized within the H&E findings and validated against species-specific antibody panels.
- Discrepancies between the histologic description and the diagnosis warrant direct communication with the pathologist, as the description represents the raw evidence and should be prioritized over potentially flawed interpretations.
- The comment section of a histopathology report is vital for integrating findings, offering differential diagnoses, prognostic insights, and recommendations for further testing, and should be critically evaluated against the clinician's assessment and patient context.

---

Histopathology reports translate tissue morphology into diagnostic language, but the translation is incomplete without clinical context. This guide teaches veterinary students and practitioners how to read these reports systematically, extract the diagnostic and prognostic information they contain, and integrate that information with the patient's history, physical findings, and other laboratory data. The goal is not to make clinicians into pathologists, but to make them informed consumers of pathology services who can ask useful questions and recognize when a report does or does not answer the clinical question that prompted the biopsy.

The report is a professional communication between two clinicians: the pathologist and the attending veterinarian. Each has information the other lacks. The pathologist sees the tissue but not the patient. The clinician sees the patient but not the tissue. Effective interpretation depends on recognizing what each party contributes and where the gaps lie. A report that describes inflammation without identifying an organizm, or neoplasia without stating surgical margins, is incomplete only if the submitting clinician knows to request the missing information.

## At a Glance

| Parameter | What to Look For | Clinical Action |
|---|---|---|
| Signalment and sample site | Matches the submitted history | Confirm correct tissue was processed |
| Gross description | Size, color, consistency, number of pieces | Correlate with surgical findings |
| Morphologic diagnosis | Tissue, process, distribution, severity | Forms the basis of clinical interpretation |
| Histologic diagnosis | Disease entity or syndrome | Compare with differential list |
| Etiologic diagnosis | Identified or suspected cause | Directs specific therapy or further testing |
| Margin status | Complete, close, or incomplete excision | Determines need for re-excision or adjunctive therapy |
| Ancillary tests | Special stains, culture, PCR, immunohistochemistry | Confirms or refines the morphologic diagnosis |
| Comment section | Pathologist's interpretation and recommendations | Read last, integrates all findings |

## The Structure of the Report

Most histopathology reports follow a predictable sequence. The gross description records what the pathologist saw before processing: specimen dimensions, color, texture, and the presence of multiple tissue types. This section matters clinically because it documents whether the submitted sample matches what was removed. A 2 cm mass described grossly as a single firm nodule that yields histologic sections of only normal skin should prompt a call to the laboratory, not silent acceptance.

The microscopic description details the histologic findings in prose. This section is often the longest and the least useful to the busy clinician, but it contains the evidence for the diagnosis. Reading it confirms that the pathologist observed what the morphologic diagnosis claims. For example, a diagnosis of lymphoplasmacytic enteritis should be supported by a microscopic description of villus blunting, crypt hyperplasia, and lamina propria infiltration by lymphocytes and plasma cells. Discrepancies between description and diagnosis warrant discussion with the pathologist.

The morphologic diagnosis is a structured statement that names the tissue, the process, the distribution, and the severity. A typical example reads: "Liver: moderate, diffuse, centrilobular hepatocellular vacuolation." This format forces precision. The histologic diagnosis then translates the morphologic findings into a disease entity, such as "steroid hepatopathy" or "glycogen accumulation." The etiologic diagnosis, when present, identifies or suggests a cause. Not every report reaches this level, and the absence of an etiologic diagnosis is not a failure of the pathologist. Many diseases have characteriztic but not pathognomonic histologic patterns.

## The Diagnostic Hierarchy

Pathologists work from pattern recognition to differential diagnosis, then to a final interpretation. The clinician should follow the same logic in reverse. Start with the histologic diagnosis and ask what conditions produce that pattern. Then compare the pattern with the clinical presentation. A diagnosis of "chronic lymphoplasmacytic rhinitis" in a cat with sneezing and nasal discharge is compatible with chronic rhinosinusitis, but it does not exclude neoplasia elsewhere in the nasal cavity. Biopsy samples only what was collected, and nasal disease is notoriously patchy. In a case series of 25 cats with nasal disease, bacterial culture results were similar across inflammatory, fungal, and neoplastic groups, and treatment response in chronic rhinosinusitis did not consistently correlate with culture or susceptibility results. Histopathology, not culture, distinguished the disease categories. This illustrates why the clinician must interpret the report within the full diagnostic context instead of treating any single result as definitive.

The morphologic diagnosis uses standardized terminology that conveys information in compressed form. "Severe" and "marked" are not interchangeable, different laboratories use different severity scales, and the submitting clinician should know the convention of the laboratory they use. Distribution terms such as "multifocal," "coalescing," and "diffuse" describe the spatial pattern of the lesion and carry diagnostic weight. A multifocal hepatic necrosis suggests an infectious or toxic cause, while a diffuse hepatocellular vacuolation suggests a metabolic or endocrine disorder.

## Clinical Correlation and Its Limits

The pathologist interprets tissue, not patients. A histologic diagnosis of "chronic interstitial nephritis" does not tell you whether the patient is azotemic, polyuric, or normotensive. That information comes from the clinician. Conversely, the clinician's history may change how the pathologist interprets the tissue. A liver biopsy showing mild portal hepatitis means something different in a dog with acute fever and elevated liver enzymes than in an asymptomatic dog whose elevated enzymes were found on a pre-anesthetic screen.

The comment section is where the pathologist integrates the histologic findings with the clinical information provided. This section often contains the most clinically useful material: differential diagnoses ranked by likelihood, recommendations for ancillary testing, and prognostic comments based on published evidence. Read this section carefully and compare it with your own assessment. Disagreement is an opportunity for dialogue, not a reason to disregard the report. Pathologists welcome questions about their interpretations, and consultation with the [Davis-Thompson Foundation veterinary pathology resources](https://www.davisthompsonfoundation.org/) can provide additional educational material for clinicians who want to deepen their understanding of specific disease processes.

## When the Report Does Not Answer the Question

A biopsy can fail to answer the clinical question for several reasons. The sample may be non-representative, too small, crushed, or from the wrong site. The lesion may be at an early stage where histologic changes are non-specific. The disease may require special stains or culture that were not performed. The pathologist should note these limitations in the report, but the clinician must recognize when the report is silent on a critical point and request clarification.

Interpretation of histopathology reports is a skill that improves with practice and feedback. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides species-specific reference material that can help clinicians correlate histologic diagnoses with clinical disease, and professional practice resources from the [American Veterinary Medical Association](https://www.avma.org/resources-tools) address the communication and quality assurance aspects of diagnostic testing. The clinician who reads reports critically, questions discrepancies, and communicates openly with the pathologist will extract the maximum diagnostic value from every biopsy.

## The Assessment Sequence

Histopathology interpretation begins before the report is opened. Reconstruct the clinical question that prompted the biopsy, then read the report against that question. A report that answers a question you did not ask is still useful, but its utility depends on recognizing the mismatch.

Work through the report in a fixed order. Start with the gross description, then the histologic description, then the morphologic diagnosis, then the histologic diagnosis, then the comment. This order matters because each section constrains the interpretation of the next. The gross description establishes what was received and how it was handled. The histologic description provides the evidence. The morphologic diagnosis translates that evidence into a lesion name. The histologic diagnosis adds clinical context. The comment reconciles the whole with your patient.

Record three things as you read: the adequacy of the sample, the certainty of the diagnosis, and the margin status where neoplasia is concerned. These three parameters drive most clinical decisions that follow.

## Reading the Histologic Description

The histologic description is the raw data of the report. It should be read as a chain of observations, not as a conclusion. Each observation should be separable from the interpretation placed on it. For example, "hepatocytes are swollen with finely vacuolated cytoplasm" is an observation. "Diffuse vacuolar hepatopathy" is an interpretation. When the description and the diagnosis disagree, trust the description and seek a second opinion.

Pay attention to distribution terms. "Focal," "multifocal," "coalescing," and "diffuse" carry different prognostic weight in different organs. A focal lesion in an otherwise normal liver biopsy has different implications than a diffuse process. The same applies to severity modifiers. "Mild," "moderate," and "marked" are semi-quantitative and vary between pathologists, but within a single report they establish a relative scale that guides monitoring.

Inflammation is described by type and distribution. Neutrophilic inflammation suggests bacterial or early injury. Lymphocytic or plasmacytic inflammation suggests immune-mediated or chronic antigenic stimulation. Eosinophilic inflammation raises the possibility of parasitism, hypersensitivity, or mast cell disease. Granulomatous inflammation suggests fungal, mycobacterial, or foreign body causes. These patterns narrow the differential list and direct ancillary testing.

## The Morphologic Diagnosis as a Decision Tool

The morphologic diagnosis is the most compressed statement in the report. It names the lesion, its distribution, and its severity in a standard format. Learn to parse this format. "Hepatic, diffuse, moderate vacuolar change" tells you the organ, the distribution, the severity, and the process. The order of terms is consistent: organ, distribution, severity, lesion.

When the morphologic diagnosis is descriptive instead of etiologic, the report is telling you that the cause cannot be determined from morphology alone. This is common in conditions with limited histologic reaction patterns. For example, chronic rhinosinusitis in cats shows similar histologic features across different underlying causes, and bacterial culture results do not consistently predict treatment response in these cases. Emming et al. found that in a case series of 25 cats with nasal disease, bacterial isolates were similar across chronic rhinosinusitis, mycotic rhinitis, and nasal neoplasia, and treatment response in chronic rhinosinusitis did not correlate with culture or susceptibility results. The histologic diagnosis in such cases narrows the field but does not identify the driver.

## Margin Assessment and Its Limits

For excisional biopsies of suspected neoplasia, margin status is a major decision point. The report should state whether neoplastic cells extend to the inked margin, approach it within a measured distance, or are separated from it by normal tissue. Read the margin statement in the context of the lesion type. A well-demarcated benign tumor with a narrow margin carries different risk than an infiltrative sarcoma with the same margin.

Margin interpretation depends on tissue handling. Retraction artifact can create false gaps between tumor and margin. Crush artifact can make true margins unreadable. The report should note when margins cannot be assessed. If the report is silent on margins, contact the laboratory before assuming they were evaluated.

The biologic behavior of the tumor type modifies how you act on margin status. A completely excised grade I mast cell tumor with clean margins may require no further therapy. The same margin status on a high-grade soft tissue sarcoma may still warrant re-excision or staging because of the tumor's propensity for microscopic extension beyond the visible margin. Consult current oncology references for tumor-specific margin recommendations.

## Ancillary Testing and the Report

Histopathology reports increasingly integrate ancillary test results. Immunohistochemistry, special stains, and molecular testing may be reported in the same document or in an addendum. Read these results in the context of the morphologic diagnosis, not in isolation.

Immunohistochemistry panels are selected based on the differential list generated from H&E morphology. A panel that returns unexpected results should prompt a conversation with the pathologist. Antibody panels vary between laboratories, and cross-reactivity differs between species. A negative result on a poorly validated antibody in an exotic species carries less weight than a negative result on a well-validated antibody in a dog or cat.

Special stains are used to confirm or exclude specific etiologies. A report that includes a comment such as "GMS stain negative for fungal organizms" is providing rule-out information. The sensitivity of the stain matters. Negative special stains do not exclude low organizm burden. The report should indicate when a negative stain is inconclusive.

## The Comment Section

The comment section is where the pathologist integrates morphology with clinical context. It may include differential diagnoses, prognostic information, or recommendations for additional testing. Read the comment critically. It is an interpretation, not a fact.

The comment may state that a lesion is of uncertain significance. This is an honest and useful statement. It tells you that the histologic findings do not map cleanly onto a known disease entity. In such cases, the clinical picture takes priority. The report becomes one piece of evidence in a larger diagnostic picture.

Some comments include recommendations for further testing. These may be appropriate or may reflect the pathologist's practice patterns. Evaluate each recommendation against your patient's situation. A recommendation for PCR testing on a tissue block may be useful in one case and unnecessary in another.

## Glossary of Common Terms

| Term | Meaning |
|------|---------|
| Hyperplasia | Increased cell number, reversible, often adaptive |
| Hypertrophy | Increased cell size, reversible, often adaptive |
| Metaplasia | Change from one differentiated cell type to another |
| Dysplasia | Disordered growth with atypia, pre-neoplastic potential |
| Neoplasia | Abnormal, uncontrolled cell proliferation |
| Anaplasia | Loss of differentiation, hallmark of malignancy |
| Invasion | Extension into surrounding tissue |
| Metastasis | Spread to distant sites |
| Necrosis | Cell death in a living organizm, usually pathologic |
| Apoptosis | Programd cell death, physiologic or pathologic |
| Fibrosis | Deposition of collagen, often a repair response |
| Granuloma | Focal aggregate of epithelioid macrophages |
| In situ | Confined to the epithelium of origin |
| Excisional biopsy | Complete removal of the lesion |
| Incisional biopsy | Partial removal for diagnosis |

Apoptosis deserves particular attention in toxicologic pathology. It is a molecular control point in the regulation of physiologic processes, toxic insults, and disease. Suppression, overexpression, or mutation of genes that orchestrate apoptosis is associated with disease, and the balance of apoptotic processes is altered in viral, autoimmune, and neurodegenerative diseases as well as in tumors. When a report describes apoptosis as a prominent feature, consider toxic exposure, immune-mediated injury, or neoplasia as potential drivers.

## Checklist for Evaluating a Report

Use this checklist for every report you receive. It is designed to catch common errors and omissions before they reach the patient.

1. Does the report identify the correct patient and tissue site?
2. Was the sample adequate for the question asked?
3. Does the histologic description support the morphologic diagnosis?
4. Is the diagnosis descriptive or etiologic?
5. If neoplasia, are margins assessed and stated?
6. Are ancillary test results consistent with the morphology?
7. Does the comment address the clinical question?
8. Are there discrepancies between sections of the report?
9. Does the report recommend additional testing, and is that recommendation justified?
10. Does the report change the treatment plan, and if so, how?

Discrepancies between sections warrant a call to the pathologist. Most laboratories welcome clinical correlation. The Davis-Thompson Foundation provides educational pathology resources and case material that can help you build skill in interpreting reports across species. The MSD Veterinary Manual offers species-specific clinical context that supports interpretation of histopathologic findings in practice.

## Recognized Failure Modes in Report Interpretation

The most common failure is treating the histologic diagnosis as a final answer instead of a hypothesis to be reconciled with the clinical picture. This error appears when a report contradicts strong clinical evidence and the clinician accepts the report without re-examination. A second failure mode is over-reading the report, assigning prognostic or therapeutic certainty to descriptive terms that the pathologist intended as provisional. A third is under-reading, where the clinician skips the histologic description and acts only on the final diagnosis line, missing important qualifiers such as "suggestive of," "cannot exclude," or "no evidence of."

Each failure mode has a detectable early sign. Contradiction between report and clinical findings should trigger a call to the pathologist, not silent acceptance. Over-reading appears when a client is given a prognosis based on a single word such as "malignant" without attention to grade, margin status, or the pathologist's stated confidence. Under-reading appears when a subsequent clinical course diverges from expectations and the original report, re-read, contains the explanation.

The table below summarizes these patterns and the discriminating check for each.

| Observation | Likely cause | Discriminating check |
|---|---|---|
| Report contradicts imaging or gross findings | Sampling error, labeling error, or genuinely discordant disease | Review the tissue collection record, confirm the site label, and contact the pathologist with the clinical findings |
| Clinician acts on the diagnosis line alone | Histologic description and comment contain qualifiers that modify the diagnosis | Re-read the description and comment, check for "suggestive of," "consistent with," or "cannot exclude" |
| Prognosis given to client before margin or grade review | Premature closure on the diagnosis | Confirm margin status, grade, and whether ancillary testing is pending before counseling |
| Repeated reports of "inflammation" when neoplasia was suspected | Biopsy sampled a reactive region adjacent to the lesion | Request deeper sections, re-biopsy, or discuss cytologic correlation with the pathologist |
| Report uses "incidental" for a finding the clinician considers significant | Different clinical context than the pathologist was given | Provide the full clinical history and ask for re-review in that context |

## Common Errors by Less Experienced Clinicians

Students and early-career clinicians frequently mistake the morphologic diagnosis for the etiologic diagnosis. A morphologic diagnosis such as "chronic lymphoplasmacytic rhinitis" describes what is present, not why it is present. The distinction matters clinically: in feline nasal disease, similar inflammatory patterns can accompany mycotic rhinitis, neoplasia, or chronic rhinosinusitis, and culture results do not reliably separate these groups, as shown in a case series of 25 cats where bacterial isolates were similar across disease categories [culture-based bacteriological examination in feline nasal disease](https://pubmed.ncbi.nlm.nih.gov/41246262/). The corrective action is to treat the morphologic diagnosis as a category, then use ancillary tests, response to therapy, and clinical progression to refine the cause.

A second common error is ignoring the distinction between a descriptive diagnosis and an interpretive one. The pathologist may write "benign mesenchymal proliferation" when cytology and histology cannot fully characterize a lesion, as reported in a canine ureteral fibroepithelial polyp where cytology suggested benign mesenchymal proliferation and histopathology provided the definitive diagnosis [cytologic and histologic diagnosis of ureteral fibroepithelial polyp](https://pubmed.ncbi.nlm.nih.gov/33332613/). The corrective action is to recognize that a descriptive diagnosis is an honest statement of limits, not a failure, and to seek the additional testing the pathologist recommends.

A third error is failing to provide the pathologist with adequate clinical context before the first interpretation. The report is only as good as the information supplied. When history is sparse, the pathologist cannot correlate findings with drug exposure, prior treatment, or known chronic disease, and the comment section will reflect that uncertainty.

## Limitations of the Evidence Base

Veterinary histopathology reporting rests on expert opinion and case experience more than on controlled trials. Many interpretive thresholds, such as what constitutes a "close" margin or how much inflammation is "significant," vary between pathologists and between institutions. The evidence base is especially thin for rare lesions, where single case reports provide the only guidance. A single case report can document a novel association, such as the acoustically evoked short latency negative response in a deaf cat with histologically confirmed cochleosaccular degeneration [ASNR in a unilaterally deaf cat](https://pubmed.ncbi.nlm.nih.gov/32586340/), but it cannot establish prevalence or predictive value. Clinicians should treat such reports as hypothesis-generating, not as practice standards.

Expert opinion still differs on how aggressively to pursue a histologic diagnosis in cases where the result is unlikely to change management. Some pathologists advocate biopsy for every mass, others argue that cytology plus clinical monitoring is sufficient for low-risk lesions. Both positions have merit, and the decision should rest on the specific patient, the lesion location, and the owner's goals.

## When to Escalate

Referral or specialist consultation is warranted when the report and clinical findings cannot be reconciled, when the lesion is rare or the diagnosis uncertain, or when the treatment decision depends on a distinction the pathologist could not make. In those situations, a second opinion from a pathologist with species or organ system expertise is appropriate. The Davis-Thompson Foundation maintains educational pathology resources and case material that can support such consultations [Davis-Thompson Foundation veterinary pathology resources](https://www.davisthompsonfoundation.org/).

Laboratory involvement is indicated when the report mentions pending ancillary tests, when deeper sections or special stains might resolve a question, or when the clinician needs guidance on additional sampling. Regulatory reporting is required when histopathology identifies a notifiable disease, a food safety concern, or a condition with trade implications. The World Organization for Animal Health publishes international standards for disease surveillance and reporting that define these obligations [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/). Clinicians should know the reporting requirements in their jurisdiction and confirm them before disposal of samples or records.

## Frequently Asked Questions

### How Much Weight Should I Give a Histopathology Report When It Conflicts With My Clinical Findings?

The report is one component of the diagnostic picture, not the final verdict. When clinical findings and histopathology disagree, first verify that the correct tissue was submitted and that the sample was representative. A small biopsy may miss a lesion, and sampling error is a recognized limitation. Re-examine the morphologic diagnosis for qualifiers such as "consistent with" or "suggestive of," which signal diagnostic uncertainty. If the discrepancy persists, contact the pathologist directly. Many institutions encourage this dialogue, and reviewing the slides together often resolves apparent conflicts. The [Davis-Thompson Foundation](https://www.davisthompsonfoundation.org/) offers educational case material that demonstrates how histologic patterns correlate with clinical presentations, which can sharpen your interpretive skills.

### What Do I Do When the Report Returns "Nondiagnostic" or "Insufficient Tissue"?

A nondiagnostic report means the sample cannot answer the clinical question, not that the lesion is absent. Common causes include crush artefact, inadequate sample size, or sampling of necrotic or hemorrhagic tissue instead of viable lesional tissue. Review the gross description to confirm what was submitted. If the lesion is accessible, repeat the biopsy and consider ultrasound guidance or surgical excision to obtain larger samples. For mass lesions, excisional biopsy is often more informative than needle-core sampling. Discuss the sampling technique with the pathologist before resubmission. In cases where repeat biopsy is impractical, such as a deep thoracic mass, weigh the risks of additional procedures against the value of a definitive diagnosis. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides species-specific guidance on biopsy techniques and sample handling.

### How Should I Interpret Incidental Findings That Are Unrelated to the Presenting Complaint?

Incidental findings are common, particularly in older animals and in necropsy submissions. A lesion such as mild lymphoplasmacytic enteritis in a cat euthanised for renal disease may have no clinical relevance. Distinguish between lesions that explain the clinical signs and those that represent background change or age-related alteration. The pathologist's comment section often addresses this distinction explicitly. If the report does not comment on clinical significance, contact the pathologist for clarification. Document incidental findings in the medical record, as they may become relevant later. For production animals, consider whether an incidental lesion has herd-level implications or affects culling decisions. The [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) provide context for lesions with reportable disease implications in livestock.

### How Do I Handle a Report That Suggests a Disease With Reportable or Zoonotic Potential?

When histopathology raises suspicion of a notifiable disease, confirm the diagnosis before acting on it. Many reportable diseases require confirmatory testing such as culture, PCR, or immunohistochemistry. Contact the relevant veterinary authority in your region for guidance on sample submission and case management. For zoonotic conditions, implement appropriate infection control measures while awaiting confirmation. Explain the situation to the owner with appropriate caution, avoiding alarm before the diagnosis is confirmed. Document all communications and actions in the medical record. The [AVMA practice resources](https://www.avma.org/resources-tools) offer guidance on zoonotic disease management and professional obligations, while the [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) outline international reporting expectations.

### How Should I Explain a Complex Histopathology Report to a Client?

Translate the morphologic diagnosis into plain language that addresses the client's concerns: what the lesion is, whether it is benign or malignant, and what it means for their animal. Avoid reading the report verbatim, as technical terms such as "pleomorphic sarcoma" or "lymphoplasmacytic infiltrate" may cause unnecessary distress. Focus on the clinical implications: prognosis, treatment options, and expected outcomes. If the diagnosis is uncertain, be honest about the limitations while emphasizing what is known. For chronic conditions where histopathology confirms a diagnosis of exclusion, such as chronic rhinosinusitis in cats, explain that the biopsy ruled out more serious diseases even if it did not identify a specific cause. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides client-friendly summaries of common conditions that can support your explanation.

### How Do I Decide Whether Additional Testing or a Second Opinion Is Worth the Cost?

Consider the clinical impact of the answer. If a second opinion would change treatment or prognosis, it is justified. If the diagnosis is clear and the therapeutic plan is unchanged, additional testing adds cost without benefit. For rare or unusual lesions, a second opinion from a veterinary pathologist with subspecialty interest may be valuable. Some institutions offer slide review services at modest cost. Discuss the value of additional testing with the owner, including the likelihood that it will alter management. In cases where histopathology is equivocal, ancillary tests such as immunohistochemistry or PCR may be more useful than a second histologic opinion. The [Davis-Thompson Foundation](https://www.davisthompsonfoundation.org/) maintains resources that can help identify pathologists with specific expertise for challenging cases.

## Related Clinical & Scientific Guides

* [Hypersensitivity Reactions: Types and Mechanisms](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/hypersensitivity-reactions-types-and-mechanisms)
* [Therapeutic Decision-Making for Respiratory Infections in Cattle](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/therapeutic-decision-making-respiratory-infections-cattle)
* [Monitoring Fluid Therapy in Critically Ill Veterinary Patients](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/monitoring-fluid-therapy-critically-ill-veterinary)


## References and Further Reading

- [Impact of culture-based bacteriological examination on diagnosis and treatment in cats with chronic nasal disease - Insights from a case series of 25 cats.](https://pubmed.ncbi.nlm.nih.gov/41246262/). 2025.
- [The acoustically evoked short latency negative response (ASNR) in a unilaterally deaf cat with histologically-confirmed cochleosaccular degeneration.](https://pubmed.ncbi.nlm.nih.gov/32586340/). 2020.
- [The effects of diisopropylmethylphosphonate, a by-product of the production of sarin and a contaminant in drinking water at the Rocky Mountain Arsenal, on female mink.](https://pubmed.ncbi.nlm.nih.gov/12726753/). 2003.
- [[Apoptosis in toxicologic pathology].](https://pubmed.ncbi.nlm.nih.gov/19999544/). 2009.
- [Chemical effects in biological systems (CEBS) object model for toxicology data, SysTox-OM: design and application.](https://pubmed.ncbi.nlm.nih.gov/16410321/). 2006.
- [The cytologic and histologic diagnosis of ureteral fibroepithelial polyp in a dog.](https://pubmed.ncbi.nlm.nih.gov/33332613/). 2020.
- [Davis-Thompson Foundation Veterinary Pathology Resources](https://www.davisthompsonfoundation.org/). Davis-Thompson Foundation.
- [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual.
- [American Veterinary Medical Association Practice Resources](https://www.avma.org/resources-tools). American Veterinary Medical Association.

## Related Articles

- [Clinical Pathology: Hematology and Biochemistry Interpretation](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/clinical-pathology-hematology-and-biochemistry-interpretation)
- [Necropsy Tissue Collection and Histopathology Submission](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/necropsy-tissue-collection-and-histopathology-submission)
- [Bacterial Culture and Sensitivity Testing: Methods and Interpretation](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/bacterial-culture-and-sensitivity-testing-methods-and-interpretation)
- [Diagnostic Cytology: Sample Collection and Interpretation](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/diagnostic-cytology-sample-collection-and-interpretation)
- [Staining Techniques in Veterinary Histopathology: H&E and Special Stains](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/staining-techniques-in-veterinary-histopathology-he-and-special-stains)

> 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.