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Skin-nontumor

Other dermatoses

Acanthosis nigricans


Reviewer: Mowafak Hamodat MB.CH.B, MSc., FRCPC (see Reviewers page)
Revised: 26 August 2011, last major update July 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Definition
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● Brown, velvety and verrucous plaques in axillae, back of neck and other skin folds, associated with visceral malignancies, endocrine diseases and congenital disorders

Clinical features
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● 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 description
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● 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
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Various images

Micro description
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● 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
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Various images

Differential diagnosis
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● Epidermal nevus
● Seborrheic keratosis
● Oral lesions may resemble Condyloma accuminta

Additional references
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eMedicine

End of Skin-nontumor > Other dermatoses > Acanthosis nigricans


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