Multiple neural fibrolipomas with macrodactyly.

Neural fibrolipoma is an uncommon tumor-like lesion that involves the upper extremity and usually arises in the median nerve. It is associated with macrodactyly in one-third of the cases. A 3-year-old girl presented with increasing size of fingers of both the hands since birth. Clinical examination revealed macrodactyly of two fingers of the right hand and three fingers of the left. Surgical reduction was performed and microscopy of the biopsy specimen established the diagnosis of neural fibrolipoma. Knowledge of the clinicopathological features is necessary for accurate diagnosis and treatment of this rare entity.

Introduction

Neural fibrolipoma, also known as fibrolipomatous hamartoma, is a rare benign tumor-like lesion which commonly involves the upper extremity and has predilection for the median nerve.[1] Other nerves affected include the ulnar, radial and brachial plexus. Clinically, it presents as a soft, slow-growing, fusiform swelling. It may be accompanied by pain, redness and diminished sensation. We report a case of multiple neural fibrolipomas in a child presenting with macrodactyly of both hands and discuss the differential diagnosis.

Case Report

A 3-year-old apparently healthy girl was brought to the orthopedics department with complaints of increasing size of fingers of both hands and swelling over left hand since birth, which was initially noticed by her mother. There was no history of any other deformity or illness associated with the hand deformity. Developmental milestones achieved were appropriate for age. On local examination, macrodactyly of index and middle fingers of right hand, and thumb, index and middle finger of left hand were noted along with elongated phalanges with palpable soft tissue mass over the left palm [Figure 1]. There was no associated tenderness, sensory loss or vascular changes. General physical examination and routine laboratory parameters were within normal limits except for low hemoglobin. Amputation of the enlarged digits was performed on two occasions at an interval of 2 months with regular monthly follow-up and the specimen sent for histopathologic examination.

Figure 1

X-ray showing hypertrophy of index, middle fingers of right hand and thumb, index and middle fingers of the left

Pathology

The excised specimen consisted of two sausage-shaped soft tissue masses which weighed 34 g together, with the larger one measuring 10 × 6 × 1 cm and the smaller one measuring 6 × 2 × 0.5 cm. Cut section showed nodular, gray-white and fatty areas. Microscopy revealed markedly thickened nerve containing nerve bundles with marked concentric thickening of epineurium and perineurium with intervening adipose tissue and fibrous stroma containing few thin-walled vascular channels [Figures 2a and b].

Figure 2a

Thickened nerve bundle with intervening adipose tissue (H and E, ×40)

Figure 2b

Nerve bundles with perineural thickening (H and E, ×40)

Discussion

Neural fibrolipoma is described as proliferation of mature adipocytes within and around the peripheral nerves. When it is associated with overgrowth of bone and macrodactyly, it is known as “macrodystrophia lipomatosa”. This condition was first described by Feriz and Barsky. It can be complicated by overgrowth in the palm, dorsum and forearm.[2] Median nerve is most commonly affected,[1] with the other affected nerves being ulnar, radial, etc.[3] However, isolated cases of cranial nerve involvement have also been reported.[4]

The clinical differential diagnoses of macrodactyly encompass numerous conditions – both acquired and congenital, ranging from dactylitis, infarction, Still's disease, osteoid osteoma, lymphangioma and hemangioma.[5]

Major clinical features of neural fibrolipomas are gigantism of a digit, hands/feet or whole extremity since birth[6] and are almost always seen during the first three decades of life. History of increasing pain, tenderness, diminished sensation, paraesthesia with enlarging mass causing compression neuropathy may be present. Carpal tunnel syndrome is a late complication seen in some cases. Imaging findings include enlargement, lipomatous infiltration and coaxial cable appearance of peripheral nerves.[4]

Grossly, neurofibrolipomas present as a soft, gray-yellow, fusiform, sausage-shaped mass that has diffusely infiltrated and replaced portions of a large nerve and its branches. The size may vary from small simple lesion to extensive complex lipomatosis involving all upper extremity nerves.[3] Histology shows mature adipose and fibrous tissue infiltrating epineural and perineural compartments. Affected nerves may also show pseudo-onion bulb and metaplastic new bone formation.[7]

The microscopic differential diagnoses include neuromas, lipomatous neurofibromas and diffuse lipomatosis. Morton's neuroma shows degenerative changes, edema and fibrosis of nerve. Lipomatous neurofibromas are smaller dermal based lesions which on microscopy show interlacing fascicles or whorls of uniform, delicate spindle cells regularly interspersed with adipose tissue.[8] In diffuse lipomatosis, there is diffuse overgrowth of mature adipose tissue which affects large portions of extremity or trunk and there is no involvement of nerves.[9]

There is no effective therapy for neural fibrolipoma. Complete excision of fibrofatty growth is contraindicated because it may cause sensory or motor disturbances.[9]

In conclusion, neural fibrolipoma with macrodactyly is a rare lesion, the clinical presentation of which can range from a small lesion to a large mass involving the entire extremity. Determination of the cause of macrodactyly is clinically difficult. Hence, knowledge of the characteristic histological and radiological findings is essential for correct diagnosis and treatment.