Neural Fibrolipoma

Definition

• Benign, localized expansion of epineurial adipose and fibrous tissue

Alternate/Historical Names

• Fibrolipomatosis of nerve
• Fibrolipomatous hamartoma of nerve
• Lipofibroma of nerve
• Lipomatosis of nerve
• Neural lipofibromatous hamartoma
• Neurolipomatosis

Diagnostic Criteria

• Surrounds and infiltrates a segment of a major nerve
  • Sausage shaped expansion
  • Most often involves upper extremity and median nerve
    • Rare cases involve ankle/foot
• Mature adipose tissue with a fibrous component
  • Epineurium expanded by adipose tissue
  • Marked, concentric perineurial thickening
    • EMA and CD34 positive
  • Separates nerve bundles
  • Metaplastic bone has been reported
• Affected nerve may show pseduo-‘onion-bulb’ like change (can be confused with intraneural perineurioma)
• May have associated bone overgrowth causing macrodactyly
  • No association with neurofibromatosis
• Usually under age 30
• Usually presents with sensorimotor deficits
• Benign but may require excision or release of compression

Jason Karamchandani MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting: 11/17/10

Differential Diagnosis

• Lipofibromatosis
• Lipoma of nerve sheath

Neural Fibrolipoma (Fibrolipomatous Hamartoma of Nerve)	Lipofibromatosis
Fat with fibrous component	Fat with cellular fibroblastic septa
Centered on and surrounds a major nerve with epineurial and perineurial thickening	Soft tissue mass, may surround nerve focally
Frequently associated with macrodactyly	Not associated with macrodactyly

Neural Fibrolipoma (Fibrolipomatous Hamartoma of Nerve)	Lipoma of Nerve Sheath
Centered on and surrounds a major nerve	Typically lacks intimate admixture of nervous and adipose tissue
Perineurial thickening	Lacks perineural thickening
Frequently associated with macrodactyly	Not associated with macrodactyly

Lists

Tumors of Peripheral Nerves

• Granular cell tumor
• Inflammatory pseudotumor
• Localized interdigital neuroma (Morton neuroma)
• Neural fibrolipoma
• Neurofibroma
• Neuromuscular choristoma
• Neurothekeoma
• Nerve cyst
• Nerve sheath myxoma
• Malignant peripheral nerve sheath tumor
• Pacinian neuroma
• Perineurioma
• Schwannoma
• Solitary circumscribed (palisaded encapsulated} neuroma
• Traumatic neuroma
  

Bibliography

• Scheithauer BW, Woodruff JM, Erlandson RA. Tumors of the Peripheral Nervous System, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 24, 1999
• Weiss, S.W., J.R. Goldblum, and F.M. Enzinger, Enzinger and Weiss' soft tissue tumors. 5th ed2008, Philadelphia, PA: Mosby Elsevier.
• Venkatesh K, Saini ML, Rangaswamy R, Murthy S. Neural fibrolipoma without macrodactyly: a subcutaneous rare benign tumor. J Cutan Pathol. 2009 May;36(5):594-6.
• Akisue T, Matsumoto K, Yamamoto T, Kizaki T, Fujita I, Yoshiya S, Kurosaka M. Neural fibrolipoma of the superficial peroneal nerve in the ankle: a case report with immunohistochemical analysis. Pathol Int. 2002 Nov;52(11):730-3.
• Silverman TA, Enzinger FM. Fibrolipomatous hamartoma of nerve. A clinicopathologic analysis of 26 cases. Am J Surg Pathol. 1985 Jan;9(1):7-14.