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Acanthosis nigricans: Signs and symptoms

What are the signs and symptoms of acanthosis nigricans?

This skin condition causes some easily recognized signs and symptoms. You may notice that your skin with acanthosis nigricans:

  • Has a brown or black discoloration

  • Feels velvety and thicker than the surrounding skin

  • Has skin tags

  • Itches

  • Has a bad odor

Acanthosis nigricans

Darker skin in the folds of the neck is common.

Acanthosis nigricans in the folds of the neck

Where acanthosis nigricans forms

A velvety, dark patch of skin can form on most areas on the body, including the:

  • Armpits

  • Back of the neck

  • Groin area (especially in skin folds and creases)

  • Elbows

  • Knees

  • Knuckles

  • Belly button

  • Woman's breasts (beneath)

  • Face

  • Female genitalia

Less often, a patch can form on the lips, mouth, eyelids, palms of the hands, bottoms of the feet, or nipples.

Acanthosis nigricans (AN) tends to appear slowly, taking months or years to form. If it appears suddenly, you should immediately make an appointment to see a board-certified dermatologist. When AN appears suddenly, it can be a warning sign of cancer.

Acanthosis nigricans

Darker, velvety skin in an armpit is another common sign.

Darker, velvety skin in an armpit is a common sign of acanthosis nigricans

Images used with permission of the Journal of the American Academy of Dermatology:

  • Image 1: J Am Acad Dermatol. 2007; 57:502-8

  • Image 2: J Am Acad Dermatol. 2007;57:907-8

Sinha S, Schwartz RA. “Juvenile acanthosis nigricans.” J Am Acad Dermatol. 2007;57:502-8.

Weger W, Ginter-Hanselmayer G, et al. “Florid cutaneous papillomatosis with acanthosis nigricans in a patient with carcinomas of the lung and prostate.” J Am Acad Dermatol. 2007;57:907-8.

Yosipovitch G, DeVore A, and Dawn A. “Obesity and the skin: Skin physiology and skin manifestations of obesity.” J Am Acad Dermatol. 2007; 56:901-16.