Synovial Myxoma: Found in Canines, Rabbits, and Now Humans Too?

CASE: A 63 year-old woman presented with a multiple-year history of right knee pain and effusions and pain refractory to numerous knee aspirations and an arthroscopic synovectomy. The patient underwent a 2-incision synovectomy and intralesional resection. A pathologic review of the specimens revealed an infiltrative tumor of basophilic, cluster of differentiation 68-positive synovial cells embedded within a myxoid stroma with low proliferative activity, most consistent with a synovial myxoma. CONCLUSIONS: This case report of a synovial myxoma-a benign, slow growing but locally aggressive mass that is most commonly found in canines-indicates that the lesion may occasionally occur in humans.