A condition characterized by discolored patches in the skin folds of the armpits, neck, or groin, ranging from tan to dark brown. Acanthosis nigricans is associated with hyperinsulinemia (a higher-than-normal level of insulin in the blood), which results from obesity-related insulin resistance. In rare cases, the condition is associated with cancer, usually of the gastrointestinal tract. Acanthosis nigricans is often an important early marker of Type 2 diabetes or evidence that a person has a high risk of developing the condition. About 90% of children who develop Type 2 diabetes have acanthosis nigricans. Any overweight person with this symptom should be tested for insulin in the blood and impaired glucose tolerance, or prediabetes. The appearance of acanthosis nigricans can usually be improved through increased physical activity and weight loss, healthy lifestyle changes that can often delay the development of Type 2 diabetes or, if diabetes is already diagnosed, help control blood glucose levels. Topical agents such as lactic acid or antifungal drugs can sometimes be used to improve a person’s cosmetic appearance.