BACKGROUND: Lipomatosis of nerve (LN) is a rare disorder characterized by the massive enlargement of peripheral nerves, frequently accompanied by generalized fibroadipose proliferation and skeletal overgrowth.
METHODS: The authors have been routinely following a 20-year-old male for lipomatosis of median nerve at the wrist noted shortly after birth. He had undergone resection of the lesion accompanied by sural nerve grafting at another institution. Clinically, although his neurological loss of function has been stable, he has had continued soft tissue growth. Serial magnetic resonance imaging has revealed persistent LN proximal to the repair sites with evidence of fatty proliferation in the sural grafts and continued LN and fatty proliferation distally. There has been a progressive circumferential pattern of fibrosis around the proximal and distal suture lines, which has a similar radiological pattern to desmoid type fibromatosis (a pattern recently described in neuromuscular choristoma [NMC] desmoid-type fibromatosis).
CONCLUSIONS: Considering the similar reaction of nerve in both LN and NMC despite differing genetic cascades, the authors believe a unifying process occurs in both lesions. The pattern of circumferential fibroproliferation would be most consistent with neuron-mediated growth from unspecified trophic factors, supporting a previously reported a nerve-derived \"inside-out mechanism.\" The clinical consequences of this unifying process are presented.

Macrodystrophia Lipomatosa (MDL) of the toe is a rare, congenital, disproportionate overgrowth involving one or more digits in the lower limb. Despite being a benign condition, when left untreated, it may cause physical impairment and interfere with daily activities. This form of localised gigantism is the result of excessive proliferation of fibroadipose tissue within the nerve along with associated macrodactyly. The mainstay of treatment is debulking or amputation to accommodate the patient\'s daily activities, as well as for cosmesis. In this case report, the clinical and radiographic findings, anatomical descriptions, and histopathological findings are presented. The difference between MDL, fibrolipomatous hamartoma (FLH) and lipomatosis of the nerve (LON) are also discussed.

Lipomatosis of nerve (LN) is a rare disorder of peripheral nerves that produces proliferation of interfascicular adipose tissue. It may be associated with soft-tissue and bony overgrowth within the affected nerve territory. LN has been almost exclusively reported in appendicular peripheral nerves; the median nerve at the wrist and palm is among the most common locations. The authors present a new pattern of LN that shows circumferential proliferation of fat around the epineurium of the nerve. They believe that this case and the two other documented examples in the literature (also affecting cervical and thoracic spinal nerves) share the same new pattern of LN. Defining the full spectrum of adipose lesions of the nerve and establishing a cause-effect relationship with nerve-territory overgrowth disorders may offer options for future management through targeted nerve lesioning.

Neural fibrolipomas are exceedingly rare benign tumors composed of hypertrophied fibrofatty tissue intermixed with nerve tissues. Our review of the published data identified only 15 cases of this tumor involving the foot and/or ankle region. An otherwise healthy 35-year-old male was referred for evaluation of a painless soft tissue mass present in the anterior left ankle. The mass had been present for approximately 6 to 7 years and had recently increased in size. Physical examination demonstrated a prominent, fluctuant mass present in the left ankle measuring 4 cm in diameter. The mass was not well-defined, was immobile, and did not transilluminate. No gross pedal deformity was present. Radiographic imaging revealed increased soft tissue prominence and density to the anterior ankle without bone involvement. Magnetic resonance imaging demonstrated a mass isointense to fat on all sequences without contrast enhancement, suggestive of a lipoma. Surgical excision was performed; the mass was yellow and lipomatous in nature. The mass was intimately associated with the superficial peroneal nerve, which had to be sacrificed during excision. The pathologic examination of the mass revealed findings consistent with a neural fibrolipoma. The patient healed uneventfully without recurrence. His only complaint was of some residual numbness in the medial foot.