Amitabh Srivastava, MD

Neurofibromas present as fusiform, uninodular or multinodular, well-circumscribed, but unencapsulated tumors.

The cut surface of neurofibroma is pale, homogeneous, waxy, and often myxoid in appearance. Degenerative changes typically seen in schwannomas are seldom present in neurofibroma.



  • Neurofibroma (NF)

  • Neurofibromatosis type 1 (NF1)


  • Von Recklinghausen disease = neurofibromatosis type 1


  • Benign peripheral nerve sheath tumor composed of Schwann cells, fibroblasts, perineurial-like cells, and residual nerves in myxoid/collagen matrix



  • Neurofibromas are sporadic in about 90% of cases; others are syndromic in association with NF1

    • NF1 results from germline mutation in NF1 gene on chromosome 17q11.2

      • NF1 gene encodes for neurofibromin protein, which is a GTPase-activating protein

      • Neurofibromin also acts as a tumor suppressor by downregulating Ras and cAMP

    • Sporadic tumors arise from somatic mutations in NF1

  • Evidence supporting neoplastic nature of NF

    • Sporadic tumors are histologically similar to NF1-associated neurofibromas

    • Tumors are monoclonal on X chromosome inactivation studies

    • Lesional cells carry NF1 gene deletion



  • Incidence

    • Most common tumor of peripheral nerve

    • NF1 incidence: 1 in 2,500-4,000 births

  • Age

    • Solitary, sporadic lesions: In patients 20-30 years old

    • Tumors in setting of NF1 present during puberty

    • Plexiform NF may be congenital

  • Gender

    • Affects both sexes equally


  • Most tumors are solitary and sporadic

  • Superficial cutaneous or localized intraneural NF present as painless, palpable mass

  • Deep intraneural tumors may present with pain or dysesthesia

  • Intraspinal (nerve root) NF may show signs of spinal cord compression

Natural History

  • Slow-growing tumors in most instances

    • Increased rates of growth may be seen in puberty and pregnancy

  • Malignant transformation in NF

    • Rare in sporadic tumors; usually occurs in setting of NF1

    • Rare in cutaneous NF (0.001%)

    • More common in plexiform NF (2-10%)

    • Clinical suspicion for malignant transformation

      • Rapid enlargement of preexisting NF

      • Pain or change in neurological symptoms


  • Surgical approaches

    • Complete resection is curative

    • Decompression of spinal cord in symptomatic tumors


  • Recurrence rare, even after partial removal


  • Localized cutaneous NF

    • Most common type

    • Nodular or polypoid, usually well circumscribed

    • Freely movable, soft, round lesions that elevate skin

    • Generally not associated with peripheral nerve

  • Diffuse cutaneous NF

    • Typically affects children and young adults

    • Large plaque-like tumors that often affect head and neck region

    • 10% associated with NF1

    • Diffuse infiltration of dermis and subcutaneous adipose tissue

    • Entraps dermal vessels, nerves, and adnexa

    • Spreads along subcutaneous connective tissue septa

  • Plexiform NF

    • Usually presents in early childhood

    • Pathognomonic of NF1 if plexiform architecture is strictly defined

    • Multinodular lesions involving multiple nerves or nerve branches

    • “Bag of worms” appearance is characteristic

    • Generally affects small nerves

    • Entire extremity may be involved (“elephantiasis neuromatosa”)

  • Massive soft tissue NF

    • Tend to be very large, diffuse, or plexiform

    • Widespread infiltration of adipose tissue and muscle

    • Result in large pendulous folds of neurofibromatous tissue (“localized gigantism”)


MR Findings

  • Irregular or bright on T2WI MR

  • Gadolinium enhancing on T1WI

  • “Target” sign due to reduced signal in intraneural NF

  • “Dumbbell” tumors: Intradural and extradural portions of paraspinal tumor acquire shape of dumbbell


General Features

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Neurofibroma

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