Acanthosis nigricans is a clinical condition consisting of a brown thickening of the skin that is symmetric. Velvety papillomatous plaques with increased skin fold markings, with papillomas, involve the axillae, base of the neck, groins, and antecubital fossa most typically. Other areas, including mucous membranes, can also be involved. Acanthosis nigricans can be secondary to an internal malignant tumor. Such a cancer is usually an adenocarcinoma, most typically gastric carcinoma.
Malignant acanthosis nigricans is usually of sudden onset and is rapidly progressive. Benign acanthosis nigricans can be secondary to obesity, insulin resistant diabetes, Stein-Leventhal syndrome, pituitary tumors, drugs such as nicotinic acid, glucocorticoids, and diethylstilbestrol, or it can be idiopathic.
- Treatment of the underlying condition results in clearing of the acanthosis nigricans.