Flexion contracture of the thumb: a malignant etiology.

A patient was first seen with a flexion deformity of the thumb interphalangeal joint that was initially diagnosed and treated as traumatic in origin. A painful forearm soft tissue mass was ultimately discovered; biopsy of the flexor pollicis longus tendon showed metastatic adenocarcinoma. Extensive evaluation failed to locate the origin of the primary tumor. Treatment consisted of local radiation and systemic chemotherapy. After 1 year, the patient is alive and well, has no evidence of disease, and refuses correction of the thumb interphalangeal flexion contracture.