http://www.histopathology-india.net/SoftTissuePath.htm

                    Path Quiz Case-65 

Fibrolipomatous hamartomas of nerve are rare, benign, fibrofatty malformations of peripheral nerves. 

Other terms applied to this condition are neural fibrolipoma, lipofibromatous hamartoma of nerves and neurolipomatosis.

Most cases occur in the first 3 decades of life (often at birth or early childhood) and a third are associated with macrodactyly which is referred to as macrodystrophia lipomatosa.

 [Congenital enlargement of one or several digits of the hands or feet (macrodactyly) is a rare disorder. The majority of the cases reported in the literature represent hamartomas with combined hypertrophy of several, predominantly lipomatous, soft tissue components and overgrowth of bone. The differential diagnosis includes Klippel-Trenaunay-Weber syndrome, neurofibromatosis, Milroy disease, and Proteus syndrome.]

Site:  The upper extremity is commonly involved with a marked predilection for the median nerve.Other sites include the lower extremity, ulnar nerve, radial nerve and brachial plexus.

Clinical presentation: It usually presents as a soft slowly growing fusiform swelling consisting of fibrofatty tissue surrounding and infiltrating major nerve and its branches (most often median and rarely ulnar nerve). Swelling may be accompanied by increasing, pain, tenderness and diminished sensation. There may be symptoms of compression neuropathy similar to carpal tunnel syndrome in some of the lesions.

Gross: The affected nerve is diffusely enlarged. Soft tan-yellow fusiform mass diffusely infiltrate and replace portions of the nerve.

Microscopic features: Image Link1 ; Image Link2 ; Image Link3 ; Image Link4

 The nerve trunk is surrounded and infiltrated by fibrofatty tissue. The epineurium of the affected nerve is expanded by fibrofatty tissue. The lesion has a diffuse infiltrative character. Nerve fascicles are well preserved. Perineural fibrosis may be present. Prolonged compression of nerves by fibrofatty tissue may result in neural degeneration and atrophy.

Differential diagnosis: Cutaneous lipomatous neurofibroma: Am J Dermatopathol. 2002 Jun;24(3):246-50  

Neuroma and neurofibroma: In fibrolipomatous hamartoma there is atrophy rather than proliferation of neural elements.

Diffuse lipomatosis: This is a lesion of subcutis and muscle and only secondarily affects nerves.

Treatment: There is no effective treatment for this lesion. Biopsy of the mass will establish the diagnosis. Excision of the lesion is contraindicated because it may lead to significant sensory and motor disturbances.