Alveolar rhabdomyosarcoma in a juvenile labrador retriever: case report and literature review.

A 7 mo old Labrador retriever presented for evaluation of facial swelling associated with a 5 cm oral mass extending caudally from the upper third premolar on the left side. Cytology revealed an atypical population of round cells of undetermined origin. A diagnosis of alveolar rhabdomyosarcoma (RMS) was reached via histopathology and confirmed with positive immunohistochemical staining for desmin. In humans, RMSs have a well-described round cell cytologic appearance. Few descriptions of veterinary cases of RMS exist. This report describes the cytologic appearance of alveolar RMS in a young dog and both summarizes and compares findings throughout the veterinary and human literature.