lipOfibrOMaTOuS haMarTOMa : a rEviEw artiClE

Synonyms, Key Words, and Related Terms Lipofibromatous Hamartoma, fibrolipomatous hamartoma, intraneural hamartoma, neural fibrolipomatosis, neural fibrolipoma, extraneural fibromas, neurofibromatosis, lipomas, intraneural lipomas, macrodystrophia lipomatosas, KlippelTrenaunay-Weber syndrome, congenital lymphedema, hypertrophic mononeuritis, hereditary hypertrophic interstitial neuritis of Dejerine-Sottas syndrome. INTRODUCTION Lipofibromatous hamartoma (LFH) is a rare, fibrofatty benign tumor comprised of proliferation of mature adipoctyes within peripheral nerves forming a palapable neurogenic mass. Although LFH was first described in English literature in 1953, there are fewer than 60 documented cases in recent medical literature.1 It affects the median nerve in 66 to 80% of cases, causing pain, sensory and motor deficits in the affected nerve distribution. In the late 1950’s and into the next decade, a number of authors reported cases of extraneural fibromas causing compression neuropathy of peripheral nerves; however, they were yet to be described in relation to one another.2,3,4,5,6,7,8,9 In 1969, Johnson and Bonfigilo coined the term “lipofibromatous hamartoma”, accurately describing the entity and its relation to carpal tunnel syndrome (CTS).10 While there is an unexplained predilection for the median nerve, cases of fatty infiltration of the brachial plexus, ulnar, radial, peroneal and plantar nerves have also been reported.11,14 To date, there are several terms used to describe this condition including fibrolipomatous hamartoma, intraneural hamartoma, neural fibrolipomatosis and neuralfibrolipoma. The differential diagnosis includes ganglion cysts, vascular malformations, traumatic neuroma and lipomas.13 In 1994, Guthikonda et al. described four types of lipomatous masses which vary depending on their location within the parent nerve: soft tissue lipomas, intraneural lipomas, macrodystrophia lipomatosas and lipofibromatous hamartomas.13 clinical prObleM Patients typically present with gradually enlarging nontender lesions in the distribution of the affected nerve. Since LFH often involves the median nerve, the presentation of median nerve LFH shares considerable overlap with carpal tunnel syndrome. Affected individuals complain of numbness and tingling along the volar aspect of the wrist and hand. Motor deficits are a late finding. frequency Congenital origin of LFH with or without macrodactyly has been previously suggested, but results have been mixed. Most cases occur within the first three decades of life, with the mean age of 22.3 in isolated cases and 22.0 in cases with macrodactyly.14 Silverman and Enzinger reported 26 cases of upper and lower extremity LFH, 7 with macrodactyly and 19 without. Combining their work and subsequent studies, it was determined that there is a 2:1 female to male ratio of cases with macrodactyly and a 1:1 ratio in cases without.14,15 Complicating the scenario even further is the considerable overlap with Klippel-Trenaunay-Weber syndrome, congenital lymphedema, hypertrophic mononeuritis, and hereditary hypertrophic interstitial neuritis of Dejerine-Sottas.10 eTiOlOgy Although there have been suggestions of a congenital origin to LFH, the etiology remains unclear. Cases arising from post-traumatic incidences have been reported, all showing the characteristic fatty infiltrate on biopsy. The pathophysiology of LFH is unknown. INDICATIONS Indications for surgical intervention vary case-by-case. Due to the intimate nerve involvement, LFH is often accompanied by a degree of neurologic morbidity. If the risk of nerve damage is low and nerve involvement is minimal, surgical debulking for cosmetic reasons can be undertaken. However, in the face of advanced nerve involvement, indications for intervention are progressive and unrelenting neurological deficits. LFH most commonly affects the median nerve in 66 to 80% of cases, causing pain, sensory and motor deficits in the affected nerve distribution.2 There have also been cases of LFH affecting the brachial plexus, ulnar, radial, peroneal and plantar nerves.11,14 There is no explanation of why the median nerve is most commonly affected. A fundamental knowledge of the anatomical distribution of nerves helps distinguish LFH from Terrill P. Julien, MD, PGY-2 Resident, Harvard Combined Orthopaedic Surgery Residency Program