Case 1: Hyperkeratosis and a hyperpigmented basal layer can be appreciated. Due to the folding of the specimen, it is hard to see the papillomatosis. Acanthosis is absent or minimal.

Acanthosis nigricans is a dermatosis that may herald disorders ranging from endocrinologic disturbances to malignancy. It common connection to obesity and insulin resistance allows for diagnosis of related disorders such as type II diabetes, the metabolic syndrome, and polycystic ovary syndrome.

Histologically, the epidermis is hyperkeratotic and thrown into papillary folds (papillomatosis). However, acanthosis is minimal, so the entity's name is actually misleading. There is basal layer hyperpigmentation (Rapini).

Acanthosis nigrican presents with thickened, velvety hyperpigmented plaques, typically of the intertriginous surfaces and neck. The neck is almost invariably affected in children, and others may show a wide variability of involvement, including the axilla,eyelids, lips, vulva, mucosal surfaces, dorsal hands, and flexural areas in the groin, knees and elbow. Occasionally the lesions are pruitic.

Treatment is aimed at identifying the underlying condition. Rapid onset of acanthosis nigrans or unintentional weight loss suggest the possibility of malignany.

The skin lesions often show improvement upon alleviation of the underlying condition. Retinoids have also been employed with success.

→Associated with diabetes, other endocrinopathies and internal malignancies, especially gastric cancer.

→Histologic features include hyperkeratosis, papillomatois and basal layer hyperpigmentation. Acanthosis is minimal.