<prompt> True about acanthosis nigricansSeen in axillaIt is associated with insulin resistanceIt signifies internal malignancyAll of the above  <response>: ACANTHOSIS NIGRICANS Classification Hereditary AN HAIR-AN syndrome: Several endocrine disorders associated. HyperAndrogenism, Insulin Resistance and Acanthosis Nigricans. Benign acquired AN: Obesity associated. Earlier called pseudo AN. Drug-induced AN: Nicotinic acid, stilbestrol, coicosteroids, oral contraceptives. Malignant AN: Adenocarcinoma of stomach and genitourinary tract. Clinical Features Morphology:- Begins as hyperpigmentation and area appears diy. Gradually, skin thickens and becomes velvety. Surface of skin appears rugose and mammillated. The edge of lesion feathered. Sites of predilection:- Neck, axillae, and groins frequently. Other flexures antecubital and popliteal fossae, face sometimes; submammary folds, wrists less frequently. Associations:- Depends on type of AN: HAIR- AN syndrome: Several endocrine disorders associated. Insulin-resistant diabetes mellitus, hyperandrogenic states, Cushings syndrome Benign acquired AN: Skin tags in the major flexures. Malignant AN: Several associations: Tripe palms, Mucosal involvement, Severe itching. Investigations Rule out:- Underlying endocrinopathies. Underlying malignancies. Treatment:- Retinoic acid 0.025 topically, response often unsatisfactory. Ref:- Neena khanna; pg num:- 37,38 