LAUSR

Dear editor, Acanthosis nigricans is a skin condition characterized by symmetrical hyperpigmented, velvety, papillomatous plaques that tend to affect flexural and intertriginous areas, although it can affect any part of the body. The diagnosis of acanthosis nigricans is based on the clinical aspect of the lesions and can be classified into benign or malignant. The former is the most common and is usually associated to endocrinological disorders (type 2 diabetes, acromegaly, Cushing syndrome, hypothyroidism and insulin resistance), as well as congenital abnormalities or drugs.1 The malignant form is associated to internal neoplasms.2 Malignant acanthosis nigricans was first described in 1890 by Pollitzer, who noted an association with a gastrointestinal tumor.3 It is characterized as a paraneoplastic skin condition of intra-abdominal malignancies and, contrary to benign acanthosis nigricans, it has a sudden onset, rapid course and extensive skin involvement. Its etiology is associated to tumor-produced substances that stimulate keratinocytes, melanocytes and fibroblasts, being transforming growth factor (TGF-α) the main substance involved because it acts in the epidermis through the epidermal growth factor receptor (EGF-1).4 Even though the neoplasm most frequently associated to acanthosis nigricans is gastric adenocarcinoma (56-61%), associations with ovarian, endometrium, cervix, breast, testicle, lung, kidney, pancreatic, liver, esophagus, prostate, thyroid, pharynx carcinoma, among other, were already described.5 The malignancy can be identified before, during or after the onset of skin lesions.5 In most cases, they occur concomitantly (61.3%), however, in 17.6% of cases, the lesions occur before the malignancy and in 21% of cases, after the tumor is identified.4 We report the case of a patient with malignant acanthosis nigricans that preceded the diagnosis of the neoplasm, contributing to the early diagnosis of the tumor. Female 53-year-old patient presented with the complaint of a 5-month history of progressive brown, isolated lesions on her skin located on the axillae, between her breasts, back, buttocks and internal aspect of the thighs. The patient also complained of malaise for 1 month.