2017 ACVIM Forum Research Abstract Program

This study included 113 canine tumors that were surgically excised in the Veterinary Medical Center of the University of Tokyo between May 2009 and December 2015. On the basis of the histopathology, the following diagnoses were determined: squamous cell carcinoma in 14 dogs; hepatocellular carcinoma in 28 dogs; oral malignant melanoma in 29 dogs; lung adenocarcinoma in 16 dogs; and transitional cell carcinoma in 26 dogs. Normal tissue samples were obtained from 6 to 13 healthy dogs. Foxp3-positive Tregs in the normal and tumor tissues were examined by immunohistochemistry. Cells with clear lymphocyte morphology, distinct nuclear staining for Foxp3, and an unstained cytoplasm were classified as Tregs. Foxp3-positive Tregs were quantified in different compartments (intratumoral and peritumoral areas). For survival analysis, cases were classified as having a high or low density of Foxp3-positive Tregs according to the median Treg number in each tumor. Overall survival was compared between cases with a high Treg number and those with a low Treg number using log-rank test.