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Neurofibromatosis Type 1

  • 1. an autosomal dominant inheritance with nearly complete penetrance; the gene is located on chromosome 17q; gene product is guanosine triphosphate-activation protein that influences cell proliferation and differentiation
  • 2. Neoplasms associated with NF 1 include neurofibromas, malignant nerve sheath tumors, optic nerve gliomas, rhabdomyosarcomas, pheochromocytomas, and carcinoid tumors (carcinoid tumors found most commonly in the appendix)
  • 3. Clinical features: must have 2 or more of the following: two solitary neurofibromas or one plexiform neurofibroma; at least 6 café-au-lait spots larger than 15 mm (post puberty); at least 2 Lisch nodules (hamartomas of the iris that usually do not cause visual problems); optic glioma; osseous lesions (sphenoid dysplasia or aplasia, pseudoarthrosis, or spinal deformity); axillary freckling; or family history
    • a. Remember: Car Lights ON/OFF – Café-au-lait, Lisch nodules, Osseous lesions, Neurofibromas, Optic gliomas, Freckling, Family history
    • b. NOTE: café-au-lait spots occur in both NF 1 and NF 2 but are more common in NF 1
  • 4. plexiform neurofibromas are pathognomonic for NF 1
    • a. malignant transformation of plexiform neurofibromas in patients with NF 1 is heralded by enlargement, increasing neurologic deficit, and pain
    • b. histopathologically characterized by high nuclear:cytoplasmic ratio, necrosis, with presence of other mesenchymal tissues such as muscle, bone or cartilage in 10% of cases
  • 5. neurofibromas are circumscribed but not encapsulated with wavy spindle shaped cells in bundles of collagen; composed of fibroblasts and Schwann cells scattered throughout the neoplasm; neoplastic cells infiltrate nerve fascicles rather than displacing them; neurofibromas are immunoreactive for vimentin but S-100 immunoreactivity is patchy; collagen may be stained with PTAH

Neurofibromatosis Type 2

  • 1. Autosomal dominant inheritence with high penetrance; gene is located on chromosome 22q; much less common than NF 1; NF 2 gene product is MERLIN (Moezin-Ezrin-Radixin-Like-Protein)which is associated with membrane and cytoskeletal structures
  • 2. Neoplasms associated with NF 2: schwannomas, neurofibromas, ependymomas, gliomas, meningiomas. The meningiomas tend to be of the fibroblastic subhistology.
  • 3. Clinical features: one of the following is needed: bilateral vestibular schwannomas; first degree relative with NF 2 plus one vestibular nerve schwannoma; first degree relative with NF 2 plus meningioma, schwannoma, glioma, neurofibroma or posterior subcapsular lens opacity; or two of the following – unilateral vestibular nerve schwannoma, multiple meningiomas, multiple schwannomas, glioma, neurofibroma, posterior subcapsular lens opacity, cerebral calcification; occasionally see café-au-lait spots, cutaneous neurofibromas or plexiform neurofibromas NOTE: Lisch nodules are not seen in NF 2 but skin plaques with a raised, rough area are often seen
  • 4. Microscopically:
    • a. Schwannomas have Antoni A with spindle shaped cells and rod shaped nuclei with dense pericellular reticulin as well as Antoni B areas with stellate or spindle shaped cells with smaller nuclei, scanty surrounding reticulin loosely arranged in a myxoid stroma; may also see palisading of nuclei and Verocay bodies (sequential nuclear palisades separated by an anuclear area); a small portion of schwannomas contain melanin

NF2 associated acoustic neuroma histopathology.
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