CHARACTERIZATION OF TESTICULAR GRANULAR CELL TUMORS IN DOMESTIC RABBITS (ORYCTOLAGUS CUNICULUS)

Thirty interstitial cell tumors (ICTs) from domestic rabbits collected from Zoo/Exotic Pathology Service, Northwest ZooPath, and Cummings School of Veterinary Medicine at Tufts University were submitted for histologic review and immunohistochemistry for p53 and Ki-67 along with Periodic acid-Schiff (PAS) staining. The objectives of this cross-sectional study were: (1) to determine the prevalence of testicular granular cell tumors (GCTs) in domestic rabbits within ICTs using PAS staining, and (2) to evaluate morphologic criteria and immunohistochemical expression of Ki-67 and p53 to prognosticate testicular ICTs, in domestic rabbits. The prevalence of ICTs was 1.93% of all submissions and 87% of all testicular tumors. All cases histologically diagnosed as ICT were reclassified as GCT based on PAS staining. Neither labeling for p53 nor the Ki-67 index was prognostically significant. Median survival time of rabbits diagnosed with GCTs was 599 days. No metastatic disease was reported in rabbits diagnosed with ICTs following surgical removal. This study found that the majority of ICTs in rabbit testicles are GCTs and staining with PAS is required to confirm the diagnosis. Regardless, surgical removal (castration) of domestic rabbits with GCTs is an appropriate treatment for this disease and no further investigation is required. Copyright 2018 Elsevier Inc. All rights reserved.