A prospective evaluation of the impact of second-opinion histopathology on diagnostic testing, cost and treatment in dogs and cats with cancer

A retrospective comparison of first and second opinion histopathology with patient outcomes in veterinary oncology cases (2011-2019)

Mandatory second opinion histopathology is common practice in human surgical pathology. It is intended to confirm the original diagnosis or identify clinically significant discrepancies, which could alter the course of disease, cost of treatment, patient management or prognosis. This retrospective analysis aimed to evaluate agreement between first and second opinion histopathology cases, examine their correlation with natural history of disease and investigate the rationale for pursuing this test. Medical records from 2011 to 2019 were reviewed, identifying 109 cases where second opinion histopathology was sought. Reasons for seeking second opinion and clinical disease course were also reviewed to determine whether case progression favoured first or second opinion findings in cases of diagnostic disagreement. Diagnostic disagreement was found in 49.5% of cases. Complete diagnostic disagreement (a change in degree of malignancy or tumour type) occurred in 15.6% cases and partial disagreement (a change in tumour subtype, grade, margins and mitotic count) occurred in 33.9%. Major disagreement (a change in diagnosis resulting in alteration of treatment recommendations) occurred in 38.5% of cases. The most common reasons for seeking second opinion were an atypical/poorly differentiated tumour (31.2%; 34/109) or a discordant clinical picture (24.8%; 27/109). Among cases with any form of disagreement, natural history of disease favoured second opinion findings in 33.3%. The first opinion was favoured over the second in a single case. These findings reinforce previous literature supporting a role for second opinion histopathology in optimizing therapy and predicting outcomes in veterinary oncology, particularly in cases where diagnosis is in question based on the overall clinical picture.

Refining the "double two-thirds" rule: Genotype-based breed grouping and clinical presentation help predict the diagnosis of canine splenic mass lesions in 288 dogs

Prediction of the likely histopathological diagnosis of canine splenic masses can guide appropriate decision-making. This study explores the predictive effect of breed and clinical presentation on the diagnosis of a canine splenic mass. Records from the Royal Veterinary College, United Kingdom (2007-2017) were reviewed. Dogs with a histopathologic or cytologic diagnosis from a splenic mass, or imaging findings consistent with disseminated metastatic disease, were included. Signalment, physical examination, haematology results, imaging findings and pathology reports were recorded. Breeds were grouped according to several permutations of their phenotype and then by clustering of breeds based on single nucleotide polymorphism analysis. Binary logistic regression was performed to identify predictors of malignancy and haemangiosarcoma. Two hundred and eighty-eight dogs were identified: 27% female and 63% male, 21% entire and 79% neutered; German Shepherd was the most common breed (11%). Median age was 10 years and median bodyweight 25 kg. Thirty-eight percent of dogs presented with haemoabdomen; a splenic mass was found incidentally in 28%. Sixty percent had a malignant tumour of which haemangiosarcoma comprised 66%. On multivariable analysis, genotype-based breed group (P = .004), haemoabdomen (P < .001) and neutrophil count (P = .025) predicted malignancy, and genotype-based breed group (P < .001) and haemoabdomen (P < .001) predicted haemangiosarcoma. Genotype-based breed group and occurrence of haemoabdomen may have predictive value to diagnose malignant splenic masses and more specifically haemangiosarcoma. The effect of genotype-based breed grouping was a superior predictor of the diagnosis of a canine splenic mass lesion compared with all phenotype-based groupings tested.

Evaluation of Region of Interest Digital Cytology Compared to Light Microscopy for Veterinary Medicine

Digital microscopy (DM) has been employed for primary diagnosis in human medicine and for research and teaching applications in veterinary medicine, but there are few veterinary DM validation studies. Region of interest (ROI) digital cytology is a subset of DM that uses image-stitching software to create a low-magnification image of a slide, then selected ROI at higher magnification, and stitches the images into a relatively small file of the embedded magnifications. This study evaluated the concordance of ROI-DM compared to traditional light microscopy (LM) between 2 blinded clinical pathologists. Sixty canine and feline cytology samples from a variety of anatomic sites, including 31 cases of malignant neoplasia, 15 cases of hyperplastic or benign neoplastic lesions, and 14 infectious/inflammatory lesions, were evaluated. Two separate nonblinded adjudicating clinical pathologists evaluated the reports and diagnoses and scored each paired case as fully concordant, partially concordant, or discordant. The average overall concordance (full and partial concordance) for both pathologists was 92%. Full concordance was significantly higher for malignant lesions than benign. For the 40 neoplastic lesions, ROI-DM and LM agreed on general category of tumor type in 78 of 80 cases (98%). ROI-DM cytology showed robust concordance with the current gold standard of LM cytology and is potentially a viable alternative to current LM cytology techniques.

Histologic processing artifacts and inter-pathologist variation in measurement of inked margins of canine mast cell tumors

Although quantitative assessment of margins is recommended for describing excision of cutaneous malignancies, there is poor understanding of limitations associated with this technique. We described and quantified histologic artifacts in inked margins and determined the association between artifacts and variance in histologic tumor-free margin (HTFM) measurements based on a novel grading scheme applied to 50 sections of normal canine skin and 56 radial margins taken from 15 different canine mast cell tumors (MCTs). Three broad categories of artifact were 1) tissue deformation at inked edges, 2) ink-associated artifacts, and 3) sectioning-associated artifacts. The most common artifacts in MCT margins were ink-associated artifacts, specifically ink absent from an edge (mean prevalence: 50%) and inappropriate ink coloring (mean: 45%). The prevalence of other artifacts in MCT skin was 4-50%. In MCT margins, frequency-adjusted kappa statistics found fair or better inter-rater reliability for 9 of 10 artifacts; intra-rater reliability was moderate or better in 9 of 10 artifacts. Digital HTFM measurements by 5 blinded pathologists had a median standard deviation (SD) of 1.9 mm (interquartile range: 0.8-3.6 mm; range: 0-6.2 mm). Intraclass correlation coefficients demonstrated good inter-pathologist reliability in HTFM measurement (κ = 0.81). Spearman rank correlation coefficients found negligible correlation between artifacts and HTFM SDs ( r ≤ 0.3). These data confirm that although histologic artifacts commonly occur in inked margin specimens, artifacts are not meaningfully associated with variation in HTFM measurements. Investigators can use the grading scheme presented herein to identify artifacts associated with tissue processing.

Agreement Between Cytology and Histopathology for Regional Lymph Node Metastasis in Dogs With Melanocytic Neoplasms

Melanocytic neoplasms are common in dogs and frequently occur within the oral cavity or in haired skin. The behavior of melanocytic neoplasms is variable and depends on tumor location, size, and histopathologic features. This study compared cytopathology and histopathology of 32 lymph nodes from 27 dogs diagnosed with melanocytic neoplasms. Agreement between the original cytology report, cytology slide review, original histopathology report, and histopathology slide review was determined for each lymph node. A subset of lymph nodes was subjected to immunohistochemistry (Melan-A) and additional histochemical stains/techniques (Prussian blue, bleach) to assist in differentiation of melanocytes and melanophages. Agreement ranged from slight to fair for each of the variables evaluated with weighted kappa (κw) or kappa (κ) analysis (original cytology vs cytology review κw = 0.24; original cytology vs original histopathology κw = 0.007; original cytology vs histopathology review κw = 0.23; cytology review vs original histopathology κw = 0.008; cytology review vs histopathology review κw = 0.006; and original histopathology vs histopathology review κ = 0.18). The diagnoses (metastatic, equivocal, or negative for metastasis) of the original report and slide review for both cytology and histopathology were not significantly correlated with survival in this population of patients. Overall, agreement between cytology and histopathology was poor even with a single clinical or anatomic pathologist performing slide review. Consensus between routine cytology and histopathology for staging of lymph nodes in patients with melanocytic neoplasms is poor and does not correlate with survival.

Surgical margins in the veterinary cancer patient

In veterinary oncologic specimens, histopathology is the gold standard for determining adequacy of excision. Despite limitations of this technique, the pathologist's interpretation of margin status significantly impacts patient management, including indications for adjuvant therapy. This article aims to summarize peer-reviewed literature as it relates to histologic margin evaluation in veterinary cancer patients. The value of histologic tumour-free margins and technical factors influencing histopathologic margin outcomes are also discussed. We review alternative strategies for determining excisional status, and discuss how an evolving understanding of tumour biology might inform clinical and research perspectives on surgical margins. In doing so, we aim to provide context and a stimulus for future investigations into this important yet incompletely understood topic.