How to Request a Second Pathology Opinion on Your Pet's Biopsy
Ask your vet about a second biopsy review for your dog or cat: who holds the slides and blocks, what re-reading can change, and how requests and costs work.
Yes. You can ask your veterinarian for a second pathology opinion on your dog's or cat's biopsy. Another veterinary pathologist reviews the tissue slides, usually with the original report and clinical history. Start by asking your veterinary team what question needs resolving and whether consultation with the original laboratory or a formal external review would help. The request normally travels through the clinic; specimen release and submission rules depend on the laboratories involved.
A review can confirm the diagnosis or change details such as tumor grade, subtype, invasion, or margin interpretation. Veterinary oncology studies have found clinically consequential differences, but their results describe referred cases that underwent review, not the probability that any pet's biopsy is wrong. A second report is also not automatically more accurate. The useful goal is to understand whether additional pathology information would change your pet's care.
This guide covers review of tissue already collected, who holds the slides and paraffin blocks, and how to organize the request. A second clinical opinion from an oncologist considers the overall care plan; a second pathology opinion examines the biopsy diagnosis. They can complement each other. Discuss review timing with your veterinarian rather than postponing prescribed care or changing treatment while waiting.
What a Second Pathology Opinion Reviews
Histopathology examines tissue structure in thin, stained sections. It differs from cytology, which examines cells collected in an aspirate or other cellular sample. A biopsy can be a small sample of a lesion or an excision of a whole mass. The kind of specimen collected affects what the report can establish: a diagnostic sample does not provide the same opportunity to assess surgical removal as a properly identified excision specimen. VCA: cytology, biopsy, and histopathology.
If your pet has an inconclusive aspirate rather than a tissue biopsy, our guide to nondiagnostic cytology covers that earlier decision. Here, the focus is an existing histopathology report and the laboratory materials used to produce it.
In routine biopsy preparation, tissue is preserved, processed, embedded in paraffin wax, and cut into thin sections for microscope slides. You do not need to learn laboratory processing techniques to request a review. You do need to distinguish the materials, because reviewing an original stained slide, cutting a new section, and testing tissue from a block are different tasks.
Original stained slide: the glass slide carrying a tissue section that the first pathologist examined. H&E means hematoxylin and eosin, a routine tissue stain.
Paraffin block: the preserved tissue embedded in wax. The laboratory can use tissue remaining in the block to make additional sections when needed.
Recut: a new section cut from the block. It comes from a different tissue level and can show features absent from the original slide.
Unstained slide: a tissue section mounted on glass without the routine stain. Receiving laboratories may request these for additional diagnostic testing.
Scrolls: sections from the block collected in tubes rather than mounted on slides. Some specific testing workflows request them; they are not a universal requirement for a second opinion.
The original report and a useful clinical history should accompany a review request. The history should identify the pet, biopsy site, lesion progression, previous tests and treatment, and what the clinician wants clarified. Surgical notes and the explanation of specimen orientation or margin markings may matter. Supplying this context lets the pathologist relate the tissue findings to the clinical question; it does not guarantee that the specimen can answer every question. Kamstock et al.: biopsy submission and reporting guidance.
When a Review Is Worth Discussing: What the Evidence Shows
An unexpected result, an atypical or poorly differentiated tumor, or a mismatch between the clinical picture and the pathology report can justify a conversation about review. This does not mean that a pet who appears well cannot have a malignant tumor. Ask the veterinarian to identify the actual discrepancy and explain what a different interpretation would change.
Regan and colleagues' 2010 retrospective study compared first- and second-opinion histopathology reports in 430 cancer cases involving dogs and cats. Diagnostic agreement occurred in 70%. Partial disagreement occurred in 20%, including changes in grade or lymphatic or vascular invasion. Complete disagreement occurred in 10%: 7% involved the degree of malignancy and 3% the cell type. Review prompted a change in treatment or prognosis in 17% of the cases evaluated. Regan et al., 2010.
A prospective study by Regan and colleagues, first published online in 2013 and appearing in the journal's 2015 issue, evaluated 52 tumors over one year. Agreement was reported in 52%, partial disagreement in 29%, and complete disagreement in 19%. Major disagreements that would affect treatment or prognosis occurred in 37%; minor disagreements occurred in 21%. The study also found differences in the costs of ideal staging and treatment recommendations. That is not proof that review always saves money. Regan et al., 2015 (online 2013).
Laliberté and colleagues' retrospective study, published online in 2021 and in a 2022 journal issue, examined 109 oncology cases from 2011–2019. Any diagnostic disagreement occurred in 49.5%, comprising 33.9% partial and 15.6% complete disagreement. Major disagreement, defined as a diagnostic change altering treatment recommendations, occurred in 38.5%. The most common recorded reasons for seeking review were an atypical or poorly differentiated tumor (31.2%) and a discordant clinical picture (24.8%). Those reasons help explain why this reviewed group cannot stand in for all biopsies. Laliberté et al., 2022 (online 2021).
| Study and design | Cases | Diagnostic agreement | Partial / complete disagreement | Reported clinical consequence |
|---|---|---|---|---|
| Regan 2010; retrospective | 430 | 70% | 20% / 10% | 17%: change in treatment or prognosis |
| Regan 2015, online 2013; prospective | 52 tumors | 52% | 29% / 19% | 37%: major disagreement affecting treatment or prognosis |
| Laliberté 2022, online 2021; retrospective | 109 | 50.5% (100% minus 49.5% disagreement) | 33.9% / 15.6% | 38.5%: change altering treatment recommendations |
These figures measure different things. Partial versus complete disagreement describes how the diagnoses differ. Major versus minor disagreement describes the consequence of the difference. A change in grade can be classified as partial diagnostic disagreement while still changing a treatment recommendation. The two classifications overlap, so their percentages should not be added together. Each study's clinical-consequence column also retains that study's definition rather than treating prognosis changes and treatment changes as identical outcomes.
The studies differ in size, design, period, and referral population. Two were retrospective; the prospective study included only 52 tumors. Their percentages are descriptive findings, not a pooled estimate or a personal forecast. The largest study's 70% agreement is a useful counterweight to the disagreement figures: review often confirms the original diagnosis. None of these reports supplies a reliable error rate for every routine biopsy in general practice, every tumor type, or every laboratory.
The practical question is whether the uncertain finding matters for your pet. Ask: 'If the diagnosis stays the same but the grade, subtype, or margin interpretation changes, how would our options change?' A confirmed diagnosis can still help planning, while a wording difference may have little effect on care. Your veterinarian can explain which report features are consequential in this particular case without promising that review will reverse the result.
Who Holds the Specimens, and Who Requests the Review?
The laboratory that processed the biopsy is the starting point for locating the slides, blocks, and any remaining unprocessed tissue. Release and retention policies vary. Cornell's Animal Health Diagnostic Center states that samples must be submitted through a licensed veterinarian, with rare exceptions requiring prior approval and arrangements. This is Cornell's submission policy, not a universal legal rule about an owner's rights to tissue or records. Cornell AHDC: submission FAQ.
Ask the clinic that submitted the biopsy to locate the accession number, contact the reporting laboratory, and coordinate with the receiving service. If another veterinarian is now managing the case, ask the two practices to arrange the handoff. A copy of a pathology report is not the same thing as transferring the physical slides or block. Our veterinary records transfer guide covers the broader chart-transfer task; specify separately that this request concerns pathology materials.
You can express the concern simply: 'I want to understand this biopsy result before we choose the next step. Could you discuss it with the reporting pathologist and explain whether a second review would help?' Ask who will submit the request, receive the report, and discuss it with you. This creates a clear route for follow-up without placing the owner in charge of laboratory handling or clinical interpretation.
Start with the Original Laboratory
Kamstock and colleagues' ACVP Oncology Initiative guidance, endorsed by WSAVA, recommends clinician–pathologist communication when the report does not match the clinical impression. Discussion may clarify wording, correct an error, or lead to further evaluation. The paper describes internal second opinions as the most common route and distinguishes informal colleague review from a formal review with an independently signed report. These are professional recommendations, not a mandate that every case must follow the same sequence. Kamstock et al.: postreport options.
Antech advertises internal second opinions and advanced case reviews, often at no extra cost, and says its reports include the pathologist's contact information. It also offers optional live slide reviews and teams with particular biopsy interests. The word 'often' matters: confirm the fee and the requested service for the case rather than assuming that every review, additional stain, or external consultation is included. Antech: pathology services.
IDEXX states that pathology consultation is complimentary for its customers, including before submission, and directs clinicians to the pathologist's email or phone number on the case report after submission. That supports starting a conversation with the reporting pathologist. It does not establish a free external review or a guaranteed completion time for additional tests. IDEXX: pathology services.
Ask whether the result of the discussion will be a clarification, an addendum, or a separately signed second-opinion report. Also ask whether another pathologist will assess the same slides or whether new sections or tests are being proposed. If the clinical question remains unresolved, an external review may be appropriate. Ask the service handling your pet's request for its expected completion time; clarification and additional testing can involve different schedules.
Slides, Blocks, and Recuts: What Gets Transferred
The Kamstock guideline recommends second-opinion review of the same slides evaluated by the first pathologist. A new section from a different block level may contain different features, so a discrepancy can reflect a difference in sampled tissue as well as interpretation. The guideline also acknowledges that some laboratories retain original slides or blocks and send recuts instead. Ask what will actually be supplied and ensure that the receiving pathologist knows whether it is the original slide or a recut. Kamstock et al.: second opinions.
| Material | What it contributes | Custody or transfer question |
|---|---|---|
| Original stained slides | Comparison of the tissue sections initially read | Can the original lab release them, and which slides were reviewed? |
| Paraffin block | Tissue for additional sections or indicated tests | Is release possible, and does the receiving lab need the block? |
| Recuts / unstained slides | New sections for review or additional testing | Which block and tissue level do they represent, and what preparation is required? |
| Remaining wet tissue | Potential additional sampling of the original specimen | Does any remain, and can the lab preserve it pending discussion? |
| Original report and clinical history | Case identity, prior findings, and the question to resolve | Has the clinic sent the complete report and relevant surgical context? |
Receiving laboratories set requirements for the specific service ordered. Kansas State's instructions for tumor panels performed on a biopsy processed elsewhere request the block with the best representative tumor sample. If the block cannot be sent, they request six unstained slides and two tubes containing five scrolls each, plus the previous biopsy report. This is a tumor-panel instruction; it should not be copied as a universal slide-review checklist. Kansas State: histopathology and IHC submission instructions.
VDx's instructions for PARR testing on an already evaluated biopsy recommend an FFPE block or at least ten unstained slides on positively charged glass, with an H&E-stained slide for each block. PARR is additional diagnostic testing, not a synonym for a routine second opinion. Its page also warns that materials sent from other laboratories may be consumed during testing and cannot be returned. Before release, have the clinic confirm what will be tested and what material will remain. VDx: prior-biopsy PARR submission information.
The laboratories and clinic should arrange packaging and transfer. VDx specifically recommends cooling protection for paraffin blocks in warm-weather shipping; that is not a cooling instruction for every type of pathology specimen. Have the veterinary team follow the receiving laboratory's current instructions, confirm receipt, and ask about returning borrowed materials. Also ask whether digital whole-slide images are acceptable. A photograph of a report or a single microscope field does not establish that a service has received the material it needs for a complete review.
flowchart TD
A["Owner and veterinarian identify the review question"] --> B["Clinic contacts original laboratory"]
B --> C["Clarification or internal review as appropriate"]
C --> D{"External review needed or requested?"}
D -->|"No"| E["Document findings and discuss care plan"]
D -->|"Yes"| F["Clinic confirms receiving service, materials, fees and timing"]
F --> G["Labs coordinate slide or block transfer under their policies"]
G --> H["Review report returns to requesting clinician"]
H --> I["Compare reports, resolve uncertainty and discuss care plan"]External Review: Choosing a Service and Estimating Costs
Select the receiving service for the question being asked, rather than assuming every university laboratory provides every specialty review. UC Davis dermatopathology explicitly offers second opinions on previously prepared glass slides and lists faculty with ECVP or ACVP qualifications. It gives an expected turnaround of three working days after sample arrival for uncomplicated cases; special stains, immunohistology, or clonality workups can take longer. That estimate belongs to this service and does not include locating materials or transit time. UC Davis: dermatopathology services.
UC Davis directs clients to contact the pathology office for current fees. Obtain a case-specific estimate through your veterinary team. A routine biopsy price, a slide-consultation fee, and a molecular-testing price can cover different services. Before comparing quotations, establish whether each includes a full report, interpretation of existing stains, new sections, or additional tests. Costs depend on the service, the material available, and any additional testing; use the case estimate rather than a general price range.
The Kamstock guidance identifies possible external-review charges for recuts, H&E staining, shipping from the original laboratory, and the reviewing laboratory's fee. Ask the clinic to identify which costs apply, who bills them, and whether further testing requires another estimate. If you plan to submit an insurance claim, ask your insurer about your own policy's requirements without assuming the review will be reimbursed. Kamstock et al.: external-review charges.
Ask for two time estimates: how soon the material can reach the receiving service and how long interpretation is expected to take after arrival. Confirm whether extra work could extend the timetable and who will notify you. If a treatment decision is time-sensitive, the veterinarian should explain how to manage care while review proceeds. Laboratory turnaround is only one part of the overall wait.
Check the Reviewing Pathologist’s Qualifications
ACVP describes itself as an organization of board-certified anatomic and clinical veterinary pathologists and outlines a two-part certification examination. For a tissue biopsy, ask about the reviewing pathologist's anatomic pathology qualifications and experience with the relevant lesion. Board certification and a relevant specialty interest are useful checks; they do not eliminate every source of diagnostic uncertainty. American College of Veterinary Pathologists.
The Kamstock guideline recommends that reports identify the pathologist's qualifications and specialty and cautions that human MD pathologists are not trained in veterinary tumor pathology or terminology. Your clinic can verify the proposed reviewer and discuss whether a particular veterinary subspecialist would be helpful. Keep this check specific to the person and service rather than assuming that an institution's name alone guarantees expertise in every tumor. Kamstock et al.: pathologist qualifications.
When Two Reports Disagree
A second report is not automatically the correct one. The Kamstock guideline says disagreement may reveal a complex case and that a third opinion or additional testing, such as immunohistochemistry, may be needed. It recommends sending formal second-opinion reports to the requesting clinician and copying the original pathologist. Sharing both reports makes it possible to discuss whether the same tissue was assessed and which features explain the difference. Kamstock et al.: interpreting a second opinion.
In the 109-case Laliberté series, the natural history of disease favored the second opinion in 33.3% of cases with disagreement and favored the first opinion in one case. This finding does not validate every second diagnosis, nor does it prove that all remaining cases supported the first. The outcome observations reinforce the need to interpret conflicting reports alongside clinical follow-up rather than declaring a winner from the order in which reports arrived. Laliberté et al.: outcomes in discordant cases.
Ask the veterinarian to explain the disagreement in plain language. Is it a different tumor classification, a grade difference, a margin interpretation, or a difference between tissue levels? Which finding would change the proposed plan? Further stains, additional tissue evaluation, another review, or occasionally another biopsy may help, but none is a guaranteed tie-breaker. The veterinary team should explain the purpose and limitations of the proposed next step before you decide together.
The request is complete when the result is explained and incorporated into your pet's plan. Ask for copies of both reports and any addendum, confirm that relevant clinicians have them, and establish follow-up. A confirmed first diagnosis can provide useful reassurance; an unresolved diagnosis still needs an explicit plan for monitoring or further investigation. Neither outcome supports changing medication or canceling care without discussing it with the treating veterinarian.
Questions to Ask Your Veterinary Team
What specific finding are we asking the pathologist to clarify, and what would change in the care plan if the interpretation differs?
Which laboratory has the slides and paraffin block, and what is the accession number? Does any remaining wet tissue need to be preserved?
Can the reporting pathologist discuss the case, and would an internal review answer our question? Will it produce an addendum or a formal second report?
Which receiving service fits this biopsy question? Does it require original slides, recuts, a block, or material for a separate test?
What will be sent with the material, including the complete original report, relevant clinical history, and surgical information?
What is the total estimate, what additional tests could add charges, and how long will retrieval, transfer, and interpretation take?
Will the slides or block be returned? Could any material be consumed in testing, and who confirms receipt and later return?
Who will explain the result, share it with the original pathologist, and coordinate care if the two reports disagree?
