Rhabdomyosarcoma with Bone Invasion in a Cat

Abstract

A 12-year-old neutered male American shorthair cat presented with swelling of the left forelimb. Radiography showed bone absorption in the proximal area of the left ulna. Aspiration biopsy of the mass lesion was performed; malignant mesenchymal tumor was suspected, and the left forelimb was amputated. Gross pathologic findings revealed poorly marginated intramuscular mass with invasion to the surrounding tissue and bone.Histopathological analysis suggested that the mass lesion consisted of a solid growth of pleomorphic tumor cells with features similar to striated muscle cells. An immunohistochemical examination was performed; the tumor cells were positive for myoglobin, confirming the diagnosis of pleomorphic rhabdomyosarcoma. For four years after surgery, no evidence of recurrence or metastasis was noted.