Segmental extraneural lipomatosis of the superficial peroneal nerve: illustrative case

BACKGROUND Adipose lesions of nerve are rare tumors that can cause nerve symptoms from either intrinsic or extrinsic compression. OBSERVATIONS The authors present a case of a patient with a 10-year history of progressive, persistent leg pain and dorsal foot paresthesias/dysesthesias. Imaging revealed several nondistinct nodules of indeterminate significance along the course of the superficial peroneal nerve (SPN). Surgery demonstrated six distinct extraneural lipomas studded on a 10-cm segment of the main SPN and one of its muscular branches in the midleg. The lesions were adherent to the SPN, without an easy dissection plane; therefore, a neurectomy was performed. Histology revealed the nerve was associated with multiple extraneural lipomas with focal evidence of prior trauma. At 4 months postoperatively, the patient’s pain had resolved completely, and she was able to resume normal physical activities. LESSONS The current classification of adipose lesions of nerve includes intraneural and extraneural lipomas and lipomatosis of nerve (fibrolipomatous hamartoma). The unique features of the present case include the discrete and segmental nature of the extraneural lipomas adherent to the nerve. Its etiology is unknown, and the histology would be suggestive of either a traumatic or a degenerative process.