Fibrolipomatous hamartoma of nerve

Abstract

Cases (19) of fibrolipomatous hamartoma of nerve without macrodactyly and 7 cases with macrodactyly are discussed. Twenty-five involved the hand, wrist, palm, and finger, and 1 case involved the foot. Patients (19) had isolated fibrofatty enlargement of nerve, while 7 had macrodactyly in addition to the peripheral nerve changes. Involved nerves included the median nerve, ulnar nerve, an unidentified nerve near the elbow, and a nerve on the dorsum of the foot. Four of 9 patients with neurologic symptoms of pain or paresthesias had physical findings compatible with compression neuropathy, and 2 others were described as having carpal tunnel syndrome. Most patients had been aware of a mass for several yr. Microscopically, the lesion was characterized by fibrofatty enlargement of nerve with massive epineural and perineural fibrosis. In 2 of the cases with macrodactyly, the fibrofatty enlargement of the nerve was associated with overgrowth of bone and the surrounding subcutaneous tissues. In 1 case, the perineural fibrosis was associated with metaplastic bone. The histogenesis of fibrofatty overgrowth of nerve has been disputed. Mature fat cells have been described within the normal nerve sheath, and it is thought that proliferation of these cells leads to the fatty enlargement of the nerve and its coverings. The relationship of these neural changes of the development of macrodactyly remains controversial. Follow-up in 18 patients (69%) reveals a benign course following biopsy, limited excision, or division of the flexor retinaculum in the wrist.