VERRUCOUS NEVOID AND KERATOTIC MALIGNANT-MELANOMA - A CLINICOPATHOLOGICAL STUDY OF 20 CASES

Verrucous naevoid malignant melanoma is a recently described variant o f malignant melanoma that may be confused both clinically and histolog ically with benign lesions. This study reports the clinical and pathol ogical features of 20 such cases. These constituted 3.2% of all melano mas diagnosed in the Department of Pathology, Aberdeen University, in the period 1970-1991. They occurred more often on the back and limbs o f male patients with a mean age of 57 years. Clinical diagnosis of ben ign lesions (warty naevi, papillomas, seborrhoeic keratosis and cysts) were made in over 50% of the cases. Eight patients had metastases, se ven of whom died of their disease. Microscopically, these lesions exhi bited a spectrum of naevoid features such as symmetry, exophytic and p apilliferous growth pattern, hyperkeratosis and pseudo-epitheliomatous hyperplasia. The majority, however, showed lateral intra-epidermal sp read and were composed of large epithelioid cells exhibiting various d egrees of cellular pleomorphism. Histological classification was diffi cult, as more than 50% of the cases were initially labelled unclassifi able. The marked papilliferous architecture of these lesions made asse ssment of Breslow depth and Clark levels difficult. Initially, 10% of the cases were histologically diagnosed as benign. It is therefore imp ortant for surgical pathologists to recognize this unusual variant of malignant melanoma, as it may be confused both clinically and patholog ically with benign lesions.