Acanthosis nigricans, the skin of the neck and axillae show the typical velvety-textured brown changes.
Classification: Type 1: Hereditary Benign Acanthosis Nigricans No associated endocrine disorder.
Type 2: Benign Acanthosis Nigricans Endocrine disorders associated with insulin resistance: insulin-resistant type II diabetes mellitus, hyperandrogenic states, acromegaly/gigantism, Cushing disease, hypogonadal syndromes with insulin resistance, Addison disease, hypothyroidism.
Type 3: Pseudo-Acanthosis Nigricans Associated with obesity; more common in patients with darker pigmentation. Common in metabolic syndrome. Obesity produces insulin resistance.
Type 4: Drug-induced Acanthosis Nigricans Nicotinic acid in high dosage, stilbestrol in young males, glucocorticoid therapy, diethylstilbestrol/oral contraceptive, growth hormone therapy.
Type 5: Malignant Acanthosis Nigricans Paraneoplastic, usually adenocarcinoma of gastrointestinal or genitourinary tract; less commonly, lymphoma.
Velvety, dark-brown to gray thickening of the skin of the armpit 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.
Acanthosis nigricans: malignant Poorly defined, velvety, verrucous and papillomatous, dark chocolate-brown plaques on the medial thighs and scrotum. Similar changes were also present in the axillae and neck, and the vermilion border of the lips was covered with velvety, raspberry-like growths.
Acanthosis nigricans: malignant Verrucous and mamillated growths on the vermilion border of the lips in a patient with carcinoma of the stomach. The gastric cancer was suspected because of these raspberry-like growths, acanthosis nigricans of the major skin folds, and weight loss. There is still a suture at the site of a biopsy.
Acanthosis nigricans: tripe palm The palmar ridges of the palm show maximal accentuation, thus resembling the mucosa of the stomach of a ruminant (tripe palm).
Malignant acanthosis nigricans in (A) the axilla and (B) the mouth.
Acanthosis Nigricans of the palms (Tripe Palms). Tripe palms is rare and is usually associated with malignant acanthosis nigricans. It affects men more than women (63% versus 37%, respectively). This difference becomes more pronounced when tripe palms is seen without acanthosis nigricans, where 86% of affected individuals are men. It appears almost exclusively in adults (median age= 62 years). There appears to be no familial association or racial predilection.