Practice Essentials
Lipofibromatous hamartoma (LFH) is a rare, benign fibrofatty tumor composed of a proliferation of mature adipocytes within peripheral nerves, which form a palpable neurogenic mass. It affects the median nerve in 66-80% of cases, causing pain and sensory and motor deficits in the affected nerve distribution; this predilection remains unexplained. [1] Although LFH was first described in the English literature in 1953, fewer than 100 cases have been documented. [2, 3, 4, 5, 6, 7, 8, 9]
Starting in the late 1950s and continuing into the next decade, numerous authors reported cases of extraneural fibromas causing compression neuropathy of peripheral nerves; however, these cases were yet to be described in relation to one another. [1, 10, 11, 12, 13, 14, 15, 16, 17] In 1969, Johnson and Bonfiglio coined the term lipofibromatous hamartoma, accurately describing the entity and its relation to carpal tunnel syndrome (CTS). [7]
In addition to the unexplained predilection of LFH for the median nerve, cases of fatty infiltration of the brachial plexus, ulnar, radial, peroneal, plantar, and digital nerves have also been reported. [7, 1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] To date, several terms besides LFH have been used to describe this condition, including fibrolipomatous hamartoma, intraneural hamartoma, neural fibrolipomatosis, and neural fibrolipoma.
The differential diagnosis includes ganglion cysts, vascular malformations, traumatic neuromas, schwannomas, neurofibromas, and lipomas. In 1994, Guthikonda et al divided lipomatous masses into the following four types according to their location within the parent nerve [21] :
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Soft-tissue lipoma
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Intraneural lipoma
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Macrodystrophia lipomatosa
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LFH
Because of the infrequency of the diagnosis, researchers have been unable to perform any randomized controlled studies examining the treatment of LFH. Consequently, no standard of care has been established for this condition. Some surgeons recommend neurolysis, whereas others advocate tunnel decompression. As more cases of LFH are reported in the literature, further insight will be gained into appropriate management. [22]
Pathophysiology
The pathophysiology of LFH is unknown. The tumor is known to have an unexplained predilection for the median nerve (66-80% of cases), causing pain and sensory and motor deficits in the affected nerve distribution. [1] LFH also affects the brachial plexus, ulnar, radial, peroneal, plantar, and digital nerves. [17, 18, 19]
A fundamental knowledge of the anatomic courses of the relevant nerves helps distinguish LFH from other hand tumors. LFH typically presents with a soft mass in the body of the nerve, whereas other neoplasms may occur in other sites.
Etiology
A congenital origin of LFH, with or without macrodactyly, has been suggested, but the etiology of this condition remains unclear. LFH in the posttraumatic setting, also showing the characteristic fatty infiltrate on biopsy, has been reported.
Epidemiology
Most cases of LFH occur within the first three decades of life, with a mean age of 22.3 years in isolated cases and 22 years in cases with macrodactyly. Silverman and Enzinger reported 26 cases of upper- and lower-extremity LFH: 7 with macrodactyly and 19 without. [19]
The term macrodystrophia lipofibromatosa refers to LFH that occurs in the presence of frank macrodactyly. [23] A 2:1 female-to-male ratio has been reported for cases with macrodactyly, and a 1:1 ratio has been found for cases without macrodactyly. [19, 20]
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. [7]
Prognosis
The outcomes and prognosis of surgical therapy for LFH have ranged from loss of sensory and motor function to full return of both motor and sensory function. Numerous factors affect prognosis, including the degree of involvement, the size of tumor burden, the age of the patient, and surgical technique. [6] Because no randomized controlled studies have examined the treatment of LFH, controversy still arises regarding the most suitable approach to the problem.
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Intraoperative photograph shows lipofibromatous hamartoma and typical gross appearance. Multiple soft, gray-yellow lobulated masses (arrows) are present within epineural sheath of radial digital nerve of right index finger. Epineurium of digital nerve displays extensive perineural fibrosis. Image reprinted with permission from American Journal of Roentgenology.
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Axial T1-weighted image of 40-year-old woman who experienced several years of paresthesias in her median nerve distribution and mass in her wrist. Note pathognomonic coaxial-cable appearance of involved nerve.
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Coronal T1-weighted image of 40-year-old woman who experienced several years of paresthesias in her median nerve distribution. On coronal sectioning, lipofibromatous hamartoma is described as resembling spaghetti.
