Skin - Melanocytic tumor
Melanoma
Pigmented epithelioid melanocytoma

Author: Christopher Hale, M.D. (see Authors page)

Revised: 20 February 2017, last major update May 2013

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Pigmented epithelioid melanocytoma

Cite this page: Pigmented epithelioid melanocytoma. PathologyOutlines.com website. http://pathologyoutlines.com/topic/skintumormelanocyticpigmentedepithelioidmelanocytoma.html. Accessed August 18th, 2017.
Definition / general
  • Rare low grade variant of melanoma, first described under this name in 2004 (Am J Surg Pathol 2004;28:31)
  • Characterized by prominent pigment synthesis
Terminology
  • Controversial entity
  • Includes so called "animal type" / equine melanomas, sporadic epithelioid blue nevi and Carney complex associated epithelioid blue nevi
Epidemiology
Sites
  • Extremities are most common site, although numerous sites are affected
Clinical features
  • Mimics melanocytic neoplasms in gray horses and laboratory animals, although appears to have different molecular origin than equine melanomas (Am J Surg Pathol 2004;28:31)
  • Includes lesions previously described as epithelioid blue nevus of Carney complex (Am J Surg Pathol 2004;28:31)
  • Does not appear to be related to sun exposure
  • Nodal metastases in 46% but death from disease is rare
  • Resembles combined nevus
Case reports
Treatment
  • Conservative reexcision and sentinel lymph node sampling
Clinical images

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27 year old man

23 year old woman

Microscopic (histologic) description
  • Sheets and nodules of heavily pigmented epithelioid or spindled melanocytes in deep dermis
  • Variable atypia but no consistent high grade features
  • May have ulceration, a combined nevus or rarely necrosis
  • After bleaching, cells have abundant gray slate-like cytoplasm, round nuclei, prominent nuclear membrane and prominent nucleoli
  • Rarely 2 nucleoli or cytoplasmic inclusions
  • No / rare mitotic figures, no atypia
Microscopic (histologic) images

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Case of the Week #113:

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Various images

Positive stains
Negative stains
Molecular / cytogenetics description
  • Associated with loss of protein kinase A regulatory subunit type 1alpha (R1alpha), coded by the PRKAR1A gene, which is lost in both sporadic cases and patients with Carney complex (Am J Surg Pathol 2007;31:1764)
  • BRAF negative in 2 cases (Dermatology 2010;221:97)
Electron microscopy description
  • Abundant cytoplasm with numerous single and rare compound melanosomes
  • Frequent aberrant melanosomes
  • Large indented nucleus with prominent nuclear membrane, central nucleolus and peripheral chromatin
Differential diagnosis
  • Blue nevus: no pigmented and epithelioid cells
  • Nodular melanosis: pigmented cells are actually pigment laden macrophages