Skin-nontumor / Clinical dermatology
Other dermatoses
Acanthosis nigricans

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc., FRCPC (see Authors page)

Revised: 17 June 2016, last major update July 2011

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Acanthosis nigricans [title]

Cite this page: Acanthosis nigricans. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skinnontumoracanthosisnigricans.html. Accessed December 2nd, 2016.
Definition / General
  • Brown, velvety and verrucous plaques in axillae, back of neck and other skin folds, associated with visceral malignancies, endocrine diseases and congenital disorders
Etiology
  • Cutaneous manifestation of a diverse group of diseases
  • May occur as inherited disorder, with Down's syndrome or after ingestion of drugs
  • 80% are "benign" type, either autosomal dominant or associated with tissue resistance to insulin, including diabetes, obesity and Cushing's disease
  • 20% are associated with GI or other internal malignancies
  • Usually age 40+ years
Clinical Features
  • Brown, velvety, and verrucous plaques in axillae, back of neck and other skin folds
  • Oral mucosa (lips and tongue) affected in 25% of cases; rare involvement of esophagus
  • Hyperkeratotic lesions may develop on the palms, soles and knuckles
Clinical Images

Images hosted on PathOut servers:

Breast, courtesy of Mark R. Wick, M.D.



Images hosted on other servers:

Hyperpigmented, brownish, velvety lesions

Right neck

Micro Description
  • Orthokeratotic hyperkeratosis (not actually acanthosis) and papillomatosis of stratum spinosum
  • Hyperpigmentation of basal cell layer, but no melanocytic hyperplasia
  • Usually no dermal inflammation
Micro Images

Images hosted on PathOut servers:

Breast, courtesy of Mark R. Wick, M.D.



Images hosted on other servers:

Papillomatosis and hyperkeratosis, H&E

Differential Diagnosis
Additional References