Ossifying fibromyxoid tumor (OFMT) – A rare cause of a painful thumb

INTRODUCTION: Ossifying fibromyxoid tumor (OFMT) is an uncommon soft tissue and bone neoplasm with just over 100 cases being reported in the literature. They present as small, slow-growing asymptomatic subcutaneous nodules in the soft tissues of the trunk and extremities. PRESENTATION OF CASE: We present a case of a 25-year-old, right hand dominant gentleman who complained of a seven-year history of pain and discomfort in the dorsal aspect of the right thumb. He was unable to move his interphalangeal joint (IPJ) but had good function otherwise. Examination revealed a localized tender swelling over the dorsal aspect of the IPJ. The thumb was fixed in extension. X-ray revealed marked abnormal soft tissue swelling around the interphalangeal joint, cystic abnormalities and new bone formation. Biopsy showed fibrous tissue containing nodules of tumor with cells in a myxoid background, rounded and histiocytoid to elongated and spindle shaped. CD57, type IV collagen, smooth muscle actin were found and CD56 and EMA were focally positive. These were in keeping with ossifying fibromyxoid tumor with an atypical immunophenotype. DISCUSSION: The tumor was formally excised with the flexor pollicis longus tendon. A two-month review revealed his pain had settled. As the tumor had an atypical immunophenotype he was referred to the regional sarcoma team. CONCLUSION: OMFT can present with atypical clinical, radiological and histological features. It is managed in a multidisciplinary setting and often requires lifetime follow up to detect a recurrence given the uncertain nature of these lesions.