Mammary gland carcinoma “in situ” in a male dog: case report

Mammary gland tumors are among the most frequently diagnosed neoplasms in female dogs. However, they are rare in male dogs, with incidence ranging from 0 to 2.7% (less than 1% on average). The triggering factors in males are still obscure, but studies have shown that hormonal abnormalities, especially those associated with testicular neoplasms, predispose towards their occurrence. Among the most common histological types diagnosed in males, adenocarcinoma, papillary cystadenocarcinoma, carcinosarcoma, simple adenoma, and spindle cell sarcoma can be highlighted. However, there are no reports of carcinoma “in situ” in males and its incidence in females is low. The present study reports a case of carcinoma in situ in a 13-year-old mixed-breed male dog, comprising a mammary gland tumor associated with mastitis, together with two histologically distinct tumors in the testicles (one in each): one was a diffuse seminoma and the other, a solid interstitial cell tumor. The present report is novel because of the histology of the mammary gland tumor.