Diagnostic difficulties in pigmented villonodular synovitis. Presentation of cases.

Pigmented villonodular synovitis is a rare entity. There are limited and diffuse, intra- and extraarticular forms. In the literature, this condition has been called xanthoma, xanthogranuloma, villous arthritis, pigmented villonodular synovitis, xanthomatous giant cell tumour, giant cell tumour of tendon sheath, giant cell fibrohemangioma, benign synovioma.