Criteria for diagnosis histopathologically: Laminate and basket-woven orthokeratosis and papillomatosis of the epidermis that has a normal granular zone and that is slightly hyperpigmented in combination with an increased number of fibrocytes in a broadened papillary dermis are findings of acanthosis nigricans.
Differential diagnosis histopathologically: Confluent and reticulated papillomatosis of Gougerot and Carteaud, reticulate seborrheic keratosis, and verrucous epidermal nevus closely resemble acanthosis nigricans histopathologically.
Criteria for diagnosis clinically: Smooth, brown to skin-colored papillated plaques that are typically located in the axillae and inguinal folds in a fashion symmetrical.
Differential diagnosis clinically: There is none.
Clinicopathologic correlation: The smooth papillated plaques are reflected histopathologically by orthokeratosis and papillomatosis of the epidermis and by a broadened papillary dermis.
Options for therapy predicated on knowledge of histopathologic findings: Successful treatment of the underlying pathologic process (e.g., endocrine disease, obesity, or internal malignancies) usually leads to complete resolution of the lesions.