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Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other
Neurofibroma - Pigmented
Author: Nat Pernick, M.D, PathologyOutlines.com, Inc.
Revised: 26 October 2009, last major update - October 2009
Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.
Definition
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● Rare tumor of scattered melanin-laden cells and benign neural cells
● 1-5% of neurofibromas (Am J Surg Pathol 2000;24:331)
Sites
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● Head & neck, buttock or leg are most common sites
Clinical
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● Variable association with neurofibromatosis
● Median age 28 years, range 2-61 years
Case reports
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● 1 year old girl with pigmented plexiform neurofibroma (J Am Acad Dermatol 2007;56:862)
● 17 year old woman with hypertrichosis (J Dermatol 2009;36:541)
● 69 year old woman with forearm lesion (The Internet Journal of Dermatology 2007;5(1))
Treatment
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● Excision, do not recur
Gross description
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● No gross pigmentation
Micro description
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● Classic features of neurofibroma with loosely arranged tumor cells containing scant cytoplasm, elongated nuclei; also melanin pigment
● Shows differentiation toward mature melanin production, but melanin synthesis appears to be impaired (Hum Pathol 2005;36:871)
Micro images
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Dermal spindle cell tumor Loosely arranged tumor cells
Inset shows pigment
MelanA + S100+
Positive stains
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● Melanin producing cells: S100, MITF, Melan-A; variable tyrosinase and HMB45
● Schwann cells: S100
● Intermediate spindle cells: S100, MITF, Melan-A
Negative stains
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● c-kit / CD117
Differential Diagnosis
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● Cellular blue nevus: not associated with neurofibroma, cells have nevoid features, not neural features
● Melanotic schwannoma: not associated with neurofibroma, biphasic, rounded nuclei, diffusely S100+
● Pigmented dermatofibrosarcoma protuberans - more extensive storiform pattern, CD34 (strong), S100 negative
End of Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other > Neurofibroma > Pigmented
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