Cases and Abstracts- see what fellow vet students are working on!

By Keiko Petrosky

Tufts Cummings School of Veterinary Medicine

ABSTRACT: EVALUATING GRADING SYSTEMS FOR ACCURATE PROGNOSIS OF CANINE CUTANEOUS MAST CELL TUMORS

Keiko Y. Petrosky and Barbara J. Davis

Tufts Cummings School of Veterinary Medicine (TCSVM)

Department of Biomedical Sciences, Section of Pathology

North Grafton, MA

Cutaneous mast cell tumors are common malignant tumors in dogs, composing 10% of all canine tumor diagnoses at Tufts Cummings School of Veterinary Medicine (TCSVM), but commonly used histologic grading systems to assess MCT has limited application with respect to clinical outcome.  Recently, a 2-tiered grading system has been published to better guide prognosis.  Based on the newer criteria, we reclassified MCT with respect to outcome in (n = 402) TCSVM cases over 8 years and in (n = 54) cases with 48-month follow-up.  The Student t-test or Mann-Whitney U test was used to determine the significance of association between outcome and histological grade.  Significance of association between survival times and histological grade was analyzed using Kaplan-Meier survival curves and appropriate Cox analysis.  Although median survival time correlated with the 3-tiered assessments, most tumors (82%) were classified as grade 2 with a wide distribution of survival times.  After reclassification of all tumors to either low- or high-grade, survival times remained significantly correlated with tumor grade, including those previously classified as grade 2.  Most (94%) of the patients diagnosed with grade 2 tumors reclassified as low-grade and reached the end of the four-year time point; however the survival time for patients diagnosed with grade 2 tumors reclassified as high-grade varied significantly.  We are now evaluating additional biomarkers as tools to predict clinical outcomes.  Preliminary studies show that the traditional proliferation markers AgNOR and Ki67 and aberrant localization of KIT may be useful in further describing these high grade tumors.

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