Skin nontumor

Topic Completed: 1 August 2010

Minor changes: 7 April 2020

Copyright: 2002-2020,, Inc.

PubMed Search: Melanocytes [title]

Mowafak Hamodat, M.B.Ch.B., M.Sc.
Page views in 2019: 1,744
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Cite this page: Hamodat M. Melanocytes. website. Accessed May 28th, 2020.
Definition / general
  • Neural crest origin
  • In basal epidermis, hair follicles, most squamous mucous membranes, leptomeninges
  • The ratio of melanocytes to basal cells ranges from approximately 1 : 4 on the cheek to 1 : 10 on the limbs
  • Contain dendrites, delicate cytoplasmic processes that extend between keratinocytes
  • Upwards or lateral migration within epidermis or into papillary dermis does not necessarily indicate malignancy
  • Cytoplasm is clear due to retraction, nuclei typically are smaller and slightly more hyperchromatic than nuclei of adjacent keratinocytes, have uniform chromatin, indented nuclear contour, no nucleoli
  • Produce melanin from tyrosine, transfer it (via cytocrinia) to adjacent epithelial cells to protect against ultraviolet rays
  • Racial skin color is due to amount of melanin in keratinocytes, not number of melanocytes
Diagrams / tables

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Skin and melanocytes

Positive stains
  • Fontana - Masson, tyrosinase, S100, NSE, MelanA / Mart1, microphthalmia transcription factor, vimentin, bcl2, HMB45 (activated melanocytes)
  • Variable keratin in activated melanocytes
Negative stains
  • GFAP, neurofilament; HMB45 and keratin in resting melanocytes
Electron microscopy description
  • Melanosomes: melanin-synthesizing organelle derived from Golgi
Differential diagnosis
  • Melanoblasts: immature counterpart
  • Melanophages: macrophages with ingested melanin
Additional references
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