Abstract: Hemangiopericytoma is a soft tissue sarcoma that originate from the pericytes of the capillary wall. In this study, we described a left radiocarpal joint mass in an 11-year-old female mixed-breed dog. Iconography, cytology, histopathology, and immunohistology were used to determine the nature of the mass. X-ray imaging showed that the tumor began in soft tissue and had clear boundaries; cytology showed that the cells were spindle-shaped, with obvious nucleoli and variably sized nuclei; histopathology revealed the presence of spindle cells surrounding blood vessels; immunohistochemistry was positive for vimentin and α-SMA, and negative for desmin and S-100. The number of PCNA positive tumor cells was more than 25%. Masson trichrome staining showed that the content of collagen fibers in tumor tissue was low. The diagnosis of hemangiopericytoma was confirmed by pathology and immunohistochemistry.

Key words: canine, hemangiopericytoma, pathology, immunohistochemistry