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  • Velvety thickening and hyperpigmentation of the skin, seen chiefly on the neck, axilla, groins, and other body folds. Usually symmetric.

  • May be hyperkeratotic and associated with skin tags.

  • A cutaneous marker related to heredity, obesity, endocrine disorders (particularly diabetes), medication, and malignancy.

  • Benign and malignant types.

  • Drug-Induced Acanthosis Nigricans (AN). Can be associated with nicotinic acid, glucocorticoid therapy, oral contraceptives, insulin, protease inhibitors, testosterone, aripiprazole, and growth hormone therapy.

  • Malignant AN. Rarely can be paraneoplastic, usually gastrointestinal adenocarcinoma but also genitourinary. Oral lesions can occur in 25% to 50% of these patients.

  • Syndromic AN. Associated with a syndrome, such as hyperinsulinemia, Cushing syndrome, polycystic ovarian syndrome, Crouzon syndrome.


AGE OF ONSET More commonly in adulthood.


Most likely are caused by increased activation of growth factor receptor proteins.


Insidious onset, except malignant type, which is rapid. The first visible change is darkening of pigmentation.

SKIN LESIONS Darkening of pigmentation (Fig. 5-1). As skin thickens, it appears velvety; skin lines accentuated; surface becomes rugose, mamillated. Often has many skin tags in body folds and neck. Malignant type: Hyperkeratosis and hyperpigmentation more pronounced (Fig. 5-2A). Involvement of oral mucosa and vermilion border of lips (Fig. 5-2B). Hyperkeratosis of the palms/soles, with accentuation of papillary markings, “Tripe hands” (Fig. 5-2C).


Acanthosis nigricans Velvety, dark-brown to gray thickening of the armpits with prominent skin folds and feathered edges in a 30-year-old obese woman from the Middle East. There were similar changes on the neck, the antecubital fossae, and on the knuckles.


Malignant acanthosis nigricans (A) Verrucous, papillomatous grayish-brown plaques in groins, medial aspects of the thigh, and scrotum. Similar lesions were found on neck and all other body folds. The patient had weight loss and wasting, and gastric adenocarcinoma was found. (B) Verrucous and papillomatous growths on the vermillion border of lips. Oral mucosa was velvety with deep furrows of the tongue. (C) Tripe palms. Palmar ridges show maximal accentuation resembling the mucosa of the stomach of a ruminant.

DISTRIBUTION Most commonly, axillae (Fig. 5-1); neck (back, sides), groins (Fig. 5-2A), anogenital, antecubital fossae, knuckles, inframammary, and umbilicus. In malignant type, also periocular, perioral, mammillary, and palms (tripe palms) (Fig. 5-2C).

MUCOUS MEMBRANES Oral mucosa: Velvety texture with delicate furrows. Type 5: Mucous membranes and mucocutaneous junctions commonly involved; warty papillomatous perioral thickenings (Fig. 5-2B).

General Examination

Screen for diabetes. Malignancy workup in older patients with ...

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