Paraneoplastic Acanthosis Nigricans Maligna

Acanthosis Nigricans Maligna (ANM) is a paraneoplastic syndrome, defined as a condition that arises in association with a malignancy elsewhere in the body but without malignant nature per se¹. It’s a rare dermatopathy that occurs in men and women over age 40, without racial predilection or known familial association. Clinically, ANM showed symmetric, hyperpigmented plaques with variable amounts of epidermal hypertrophy, ranging in color from yellow to brown or black, often with overlaid papillomas. The most common affected sites are body flexures and the posterior neck, but also mucosal surface involvement is frequent and may be the only clinical symptom present². Any mucosal surface can be involved, and as regards the oral cavity, disease affects the lips, tongue, palate, buccal and gingival mucosa.

ANM is primarily associated with adenocarcinomas, mostly of gastric origin. Accordingly, the progression of the tumor will lead to a worsening of the ANM, while regress in case of tumour treatment, and resurface with recurrence and metastases.

A 62-year-old man was referred for evaluation of papillomatous lesions of the oral mucosa, appeared in previous months. The patient was diagnosed a gastric adenocarcinoma at an advanced stage 6 months before. Clinical examination showed diffuse papillomatous or wart-like areas of normal mucosal color and soft consistency involving lips, oral mucosa and hard palate. The tongue and the vestibular mucosa were thickened and furrowed. The lesions are asymptomatic. A biopsy was performed, and histopathological analysis revealed acanthosis and papillomatosis, hyperkeratosis, and lymphohistiocytic infiltrate. The patient was clinically diagnosed with ANM, according to clinical and histologic findings, and the patient’s medical history. Isotretinoin 0,05% was prescribed for local therapy. The patient did not return to follow-up due to complications of gastric adenocarcinoma, and died 6 months later.