Synovial lipoma arborescens

: The paper describes a case of synovial lipoma arborescens (tree-forming lipoma) of the knee joint. This tumor is a variety of lipomas--a benign tumor composed of mature adipose tissue without signs of atypia. Most investigators regard lipoma as a reactive rather than neoplastic process. X-ray and histological studies should be performed for its differential diagnosis with pigmented villonodular synovitis, synovial chondromatosis, synovial hemangioma, xanthoma, a group of chronic synovitis in rheumatic diseases (rheumatoid arthritis, amyloid arthropathy, psoriatic arthritis). Its final diagnosis is possible only after morphological study.