A 59-year-old woman presents with increasing pigmentation of the skin. Physical examination shows hyperkeratosis and hyperpigmentation of the axilla, neck, flexures, and anogenital region. Endocrinologic studies reveal normal serum levels of adrenal coicosteroids and glucocoicoids. If this patient's skin pigmentation represents a paraneoplastic syndrome, the primary tumor would most likely be found in which of the following anatomic locations?
High-Yield Explanation
Acanthosis nigricans is a cutaneous disorder marked by hyperkeratosis and pigmentation of the axilla, neck, flexures, and anogenital region. It is of paicular interest because more than half of patients with acanthosis nigricans have cancer. Over 90% of cases occur in association with gastrointestinal carcinomas (primarily stomach cancer). The other tumors are uncommon causes of acanthosis nigricans.