100+ Free ACVP Veterinary Pathology Practice Questions

Neoplasia & Tumor Pathology

Round cell tumors (lymphoma, MCT, histiocytoma, plasmacytoma, TVT), Patnaik 3-tier and Kiupel 2-tier MCT grading, canine lymphoma WHO classification, PARR PCR for clonality (IgH B-cell vs TCR gamma T-cell), IHC lymphoid panel (CD3, CD20, CD79a, Pax5, CD21, MUM1/IRF4), c-KIT (CD117, KIT exon 8/11 ITD in high-grade MCT), Ki-67 proliferation, feline injection-site sarcoma, hemangiosarcoma (splenic, cardiac right atrial), osteosarcoma (appendicular metaphyseal), transitional cell carcinoma (BRAF V595E).

Clinical Pathology — Hematology

Regenerative vs non-regenerative anemia, reticulocyte count, spherocytes (IMHA — slide agglutination, Coombs/DAT positive), Heinz bodies (acetaminophen toxicity in cats — methemoglobinemia, onion/garlic allium, zinc toxicosis — pennies post-1982), eccentrocytes, schistocytes (DIC, microangiopathic), Howell-Jolly bodies (splenectomy/splenic dysfunction), basophilic stippling (lead poisoning or regeneration), nucleated RBCs, leukocyte responses (neutrophilic left shift with toxic change), bone marrow cytology, Pelger-Huët anomaly, greyhound/sighthound reference intervals.

Cytology

FNA and impression smear preparation, criteria of malignancy (anisocytosis, anisokaryosis, macrokaryosis, prominent/multiple nucleoli, multinucleation, bizarre mitoses), inflammation patterns (suppurative, pyogranulomatous, eosinophilic, lymphoplasmacytic), effusions classification (transudate <2.5 g/dL protein, modified transudate, exudate — septic with degenerate neutrophils, chylous — triglycerides, neoplastic, FIP high protein low cellularity pyogranulomatous), CSF, synovial fluid, BAL/TTW, vaginal cytology (cornified superficial — estrus), India ink for Cryptococcus capsule, broad-based budding Blastomyces.

General Pathology

Reversible vs irreversible cell injury, apoptosis (caspase cascade, Bcl-2/Bax, intrinsic vs extrinsic) vs necrosis, necrosis patterns (coagulative — ischemic, liquefactive — CNS and abscess, caseous — TB/fungal, fat — pancreatitis), acute vs chronic vs granulomatous inflammation, wound healing phases, hemodynamics (Virchow's triad for thrombosis, DIC, shock — hypovolemic/cardiogenic/distributive/obstructive), neoplasia hallmarks, oncogenes and tumor suppressors (p53, Rb, APC), amyloidosis (AA reactive, AL primary, apple-green birefringence with Congo red under polarized light).

Infectious Disease Pathology

Feline infectious peritonitis (coronavirus spike gene 3c mutation enables macrophage tropism, pyogranulomatous vasculitis, wet/effusive and dry/granulomatous forms), canine distemper (eosinophilic intracytoplasmic and intranuclear inclusions in epithelium), parvovirus (intestinal crypt necrosis, lymphoid depletion), rabies Negri bodies (hippocampus and cerebellar Purkinje cells), herpesviruses (intranuclear Cowdry type A inclusions), Johne's disease (Mycobacterium avium paratuberculosis — Ziehl-Neelsen acid-fast), Blastomyces (broad-based budding), Cryptococcus (narrow-based budding with thick capsule — India ink, mucicarmine), Histoplasma (intracellular in macrophages), Aspergillus (45° septate hyphae), Pythium (broad non-septate, H&E negative — GMS positive), Toxoplasma/Neospora (Neospora more common myositis/neurologic in dogs).

Clinical Pathology — Chemistry

Hepatic enzymes — ALT (hepatocellular leakage, half-life longer in dogs vs cats), ALP (cholestasis, steroid-induced in dogs, bone isoform in growing animals, feline ALP very specific due to short half-life), GGT (cholestasis; high in colostrum of neonatal calves/foals), AST (hepatic and muscle). Hepatic function — bile acids (pre/post-prandial, portosystemic shunt), ammonia, albumin (synthetic), BUN (low in liver failure/PSS). Renal — creatinine, SDMA (earlier CKD marker), phosphorus, USG. Electrolytes — Na:K <27 suggests hypoadrenocorticism (Addison's). Hypercalcemia differentials — GOSHDARN-IT (granulomatous, osteolytic, spurious, hyperparathyroidism primary, D vitamin toxicosis, Addison's, renal, neoplasia — lymphoma/AGASACA/multiple myeloma, idiopathic cats, temperature).

Histopathology Techniques

10% neutral-buffered formalin fixation (10:1 volume ratio, penetration ~1 mm/hr, 24-48 hr for routine), alternative fixatives (Bouin's for testis/eye, Carnoy's for lipids, glutaraldehyde for EM), decalcification (EDTA preserves IHC antigenicity better than acid-based), processing dehydration/clearing/infiltration, microtomy 3-5 μm, H&E. Special stains — PAS (fungi, basement membrane, glycogen), GMS (fungi black), Ziehl-Neelsen (acid-fast bacteria red — Mycobacterium, Nocardia with modified), Giemsa (blood parasites, mast cell granules metachromatic, Helicobacter), Masson trichrome (collagen blue/green, muscle red), Congo red (amyloid — apple-green birefringence with polarization), Prussian blue/Perls (iron/hemosiderin blue), von Kossa (calcium black), reticulin (type III collagen), oil red O (lipid — frozen).

Immunohistochemistry & Ancillary Diagnostics

Lymphoid — CD3 (T-cell cytoplasmic), CD20 and CD79a and Pax5 (B-cell nuclear Pax5), CD21 (mature B and follicular dendritic), MUM1/IRF4 (plasma cells and activated B). Epithelial — pan-cytokeratin AE1/AE3, CK7/CK20 patterns, E-cadherin membranous. Mesenchymal — vimentin, smooth muscle actin, desmin, S100, myogenin/MyoD (rhabdomyosarcoma). Melanocytic — S100, Melan-A, PNL2, SOX10. Endothelial — CD31, factor VIII, von Willebrand factor (hemangiosarcoma). Proliferation — Ki-67 (MIB-1), PCNA. Mast cell — c-KIT/CD117 with pattern I membranous (better prognosis) vs II/III cytoplasmic (worse). GIST — c-KIT and DOG1. Neuroendocrine — chromogranin A, synaptophysin, NSE. Positive/negative controls, antigen retrieval (HIER citrate pH 6 vs EDTA pH 9, enzymatic).

Necropsy & Gross Pathology

Systematic postmortem examination with standard techniques per species (small animal left lateral recumbency, large animal left lateral with upper limbs reflected, equine/bovine in situ GI). External/internal inspection, organ weights, sampling for histopathology, culture (fresh sterile), toxicology (stomach content/liver/kidney frozen), ancillary tests (PCR, IHC). Fixation 10:1 formalin:tissue. Zoonotic precautions (rabies — Negri bodies and direct fluorescent antibody, anthrax — do not open carcass suspected, Brucella, Mycobacterium bovis, Yersinia pestis plague, Francisella tularensis, avian influenza HPAI). Postmortem change vs antemortem lesions (pseudomelanosis, bile imbibition, hemoglobin imbibition, hypostatic congestion). Forensic necropsy — chain of custody, photograph everything, preserve evidence.

Molecular Diagnostics

Conventional and real-time qPCR, digital droplet PCR sensitivity. PARR (PCR for antigen receptor rearrangement) — IgH heavy chain for B-cell clonality, TCR gamma for T-cell clonality (monoclonal band vs polyclonal smear — distinguishes neoplasia from reactive); limitations include false negatives and cross-lineage rearrangements. c-KIT exon 8 and 11 internal tandem duplications in high-grade mast cell tumors (worse prognosis, toceranib/masitinib tyrosine kinase inhibitor response). BRAF V595E mutation in >80% of canine urothelial/prostatic carcinomas (urine-based diagnostic test). In situ hybridization (RNAscope, FISH). Next-generation sequencing for research/clinical. Transmissible venereal tumor clonally transmitted (LINE-1 retrotransposon into c-myc — founder cell ~6000 years ago).

Parasitology

GI helminths — Toxocara canis (transplacental, transmammary, zoonotic larva migrans), hookworms (Ancylostoma — melena, regenerative anemia), Trichuris (whipworm — cecum/colon). Cestodes — Taenia, Echinococcus (zoonotic hydatid disease), Dipylidium caninum (flea intermediate). Trematodes — Fasciola hepatica (ruminant liver flukes), Paragonimus kellicotti (lung). Protozoa — Giardia trophozoites/cysts, Cryptosporidium (acid-fast oocysts), Isospora, Sarcocystis (muscle). Arthropods — Demodex cigar-shaped deep, Sarcoptes round burrowing with intense pruritus, Cheyletiella walking dandruff, Otodectes ear. Heartworm Dirofilaria immitis (adults in pulmonary arteries and right heart, microfilariae in blood — Knott's test; antigen ELISA = adult female protein).

Urinalysis

Specific gravity interpretation (dog <1.030 inappropriate if dehydrated/azotemic, cat <1.035; hyposthenuria <1.008, isosthenuria 1.008-1.012). Dipstick — protein (requires UPC confirmation; <0.2 normal dog, <0.4 cat), glucose (diabetes, proximal tubular dysfunction — Fanconi), ketones, bilirubin (trace normal in concentrated dog urine, abnormal in cats), blood (hematuria/hemoglobinuria/myoglobinuria). Sediment — casts (hyaline benign, granular/cellular tubular injury, waxy chronic), crystals (struvite/MAP coffin-lid, calcium oxalate monohydrate picket-fence and dihydrate envelope, ammonium urate in Dalmatians/PSS, cystine hexagonal — cystinuria, bilirubin). UPC, urine cortisol:creatinine, fractional electrolyte excretion.

Endocrine Pathology

Hyperadrenocorticism — PDH (pituitary-dependent ~85%) vs ADH (adrenal tumor ~15%); LDDS screening test, HDDS and endogenous ACTH to differentiate, ACTH stim. Hypoadrenocorticism (Addison's) — Na:K ratio <27, ACTH stim confirms. Diabetes mellitus — type 1 insulin-dependent dogs, type 2 with amyloidosis of islets in cats, fructosamine (2-3 week glycemic average). Thyroid — feline hyperthyroidism (adenomatous hyperplasia/adenoma, rarely carcinoma), canine hypothyroidism (lymphocytic thyroiditis autoimmune), C-cell/medullary carcinoma (calcitonin, amyloid in bulls). Parathyroid — primary HPT (functional adenoma — hypercalcemia, low phosphorus, normal/low PTHrP, high PTH). Pheochromocytoma (chromaffin cells adrenal medulla, catecholamine-secreting). Insulinoma (beta-cell — Whipple's triad).

Coagulation & Hemostasis

Primary hemostasis — platelets and von Willebrand factor; thrombocytopenia (ITP immune-mediated, infectious Ehrlichia/Anaplasma/Rickettsia, DIC consumptive, marrow). vWD type 1 Dobermans most common. BMBT screens primary hemostasis. Secondary hemostasis — PT (extrinsic — tissue factor + VII, prolonged first with rodenticide due to factor VII short half-life), aPTT (intrinsic — VIII, IX, XI, XII; hemophilia A = VIII, hemophilia B = IX, X-linked). Thrombin time, fibrinogen, D-dimers, antithrombin. DIC (consumption — thrombocytopenia, schistocytes, prolonged PT/aPTT, low fibrinogen, elevated D-dimers/FDPs). Anticoagulant rodenticide (warfarin/brodifacoum) — vitamin K1 treatment, prolonged PT first.

Cardiovascular & Respiratory Pathology

Hypertrophic cardiomyopathy — feline, MYBPC3 mutation in Maine Coons and Ragdolls, concentric LV hypertrophy with interventricular septum thickening, LA dilation predisposes to thromboembolism (saddle thrombus). Dilated cardiomyopathy — Doberman/Great Dane; Boxer ARVC (plakophilin/desmoplakin); taurine deficiency in cats historic and now implicated in some dogs with grain-free/legume-heavy diets. Myxomatous mitral valve disease (endocardiosis) — small breeds CKCS, degenerative valve, regurgitation. Bacterial endocarditis. Respiratory — feline asthma (eosinophilic airway inflammation, smooth muscle hypertrophy), canine chronic bronchitis, bacterial bronchopneumonia (cranioventral — aspiration), pulmonary edema (cardiogenic vs non-cardiogenic — ALI/ARDS), PIE/eosinophilic bronchopneumopathy, primary pulmonary carcinoma vs metastasis.