Recurrent intramuscular lipoma at extensor pollicis brevis: A case report

BACKGROUND: This report describes and discusses recurrent intramuscular lipoma (IML) of the extensor pollicis brevis (EPB). An IML usually occurs in a large muscle of the limb or torso. Recurrence of IML is rare. Recurrent IMLs, especially those with unclear boundaries, necessitate complete excision. Several cases of IML in the hand have been reported. However, recurrent IML appearing along the muscle and tendon of EPB on wrist and forearm has not been reported yet. CASE SUMMARY: In this report, the authors describe clinical and histopathological features of recurrent IML at EPB. A 42-year-old Asian woman presented with a slow-growing lump in her right forearm and wrist area six months ago. The patient had a history of surgery for a lipoma of the right forearm one year ago with a scar of 6 cm on the right forearm. magnetic resonance imaging confirmed that the lipomatous mass, which had attenuation similar to subcutaneous fat, had invaded the muscle layer of EPB. Excision and biopsy were performed under general anesthesia. On histological examination, it was identified as an IML showing mature adipocytes and skeletal muscle fibers. Therefore, surgery was terminated without further resection. No recurrence occurred during a follow-up of five years after surgery. CONCLUSION: Recurrent IML in the wrist must be examined to differentiate it from sarcoma. Damage to surrounding tissues should be minimized during excision.