Skin inflammatory (nontumor)
Keratinization disorders
Acanthosis nigricans

Author: Mowafak Hamodat, M.D., M.Sc. (see Authors page)

Revised: 22 October 2018, last major update July 2011

Copyright: (c) 2002-2018, PathologyOutlines.com, Inc.

PubMed Search: Acanthosis nigricans [title]

Cite this page: Hamodat, M. Acanthosis nigricans. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skinnontumoracanthosisnigricans.html. Accessed December 12th, 2018.
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 server:

Contributed by Mark R. Wick, M.D.

Breast



Images hosted on other servers:

Hyperpigmented, brownish, velvety lesions

Right neck

Microscopic (histologic) description
  • Orthokeratotic hyperkeratosis (not actually acanthosis) and papillomatosis of stratum spinosum
  • Hyperpigmentation of basal cell layer, but no melanocytic hyperplasia
  • Usually no dermal inflammation
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Mark R. Wick, M.D.

Breast



Images hosted on other servers:

Papillomatosis and hyperkeratosis, H&E

Differential diagnosis