Histological aspect of ARK: (A1) marked hyperorthokeratosis without dysplasia, discrete surface papillomatosis and mild acanthosis with elongated ridges, some of them anastomosed. (HES, × 10). (A2) High magnification showing a wedge-shaped hypergranulosis. (HES, × 40). (B) Squamous epithelium presenting moderate to marked acanthosis and hyperparakeratosis with some anastomosed epithelial ridges and mild focal inflammation in the subjacent conjunctive tissue. (HES, × 10). (C) Melanin in the epithelium, free and in the cytoplasm of macrophages (HES, × 40).