This week’s case is a 10-year-old male neutered domestic shorthair cat presented for a recurrent growth on right paw. Post your interpretation in the comments section!
There is severe lysis of all of the bones of the first digit of the right manus, with nearly complete destruction of the metacarpal bone and proximal phalanx. There is severe regional soft tissue swelling over the medial aspect of the right manus as well. The second metacarpal bone has thinning and irregularity of the cortex. There is a transverse fracture in the mid diaphysis of the third metacarpal bone, the margins of the fractures are irregular and there is moderate irregular periosteal proliferation present circumferentially around the fracture.
Findings in the right manus are most consistent with a aggressive soft tissue neoplasia with regional osteolysis and pathologic fracture of the third metacarpus.
Cytology report: The primary considerations include a malignant giant cell tumor of soft parts, an osteosarcoma, an atypical fibrosarcoma or, less likely, a neurofibrosarcoma (formerly malignant fibrous histiocytoma).