There is also an increased incidence in the Native American population. The incidence of AN is equal for men and women. Lesions of benign AN may be present at any age, including at birth, although it is found more commonly in the adult population. Patients usually present with an asymptomatic area of darkening and thickening of the skin. Pruritus occasionally may be present.
Lesions begin as hyperpigmented macules and patches and progress to palpable plaques.
In approximately one third of cases of malignant AN, patients present with skin changes before any signs of cancer. In another one third of cases, the lesions of AN arise simultaneously with the neoplasm. In the remaining one third of cases, the skin findings manifest sometime after the diagnosis of cancer. The posterior neck is the most commonly affected site in children. The vulva is the most commonly affected site in females who are hyperandrogenic and obese.