An 80-year-old-female patient had a pigmented lesion on: the hard palate, the soft palate, the alveolar mucosa and the vestibolar mucosa of the maxillary gingiva. Pigmented macules and patchs had been persistent and asymptomatic for many years (Fig. 1). The lesion exhibited irregularities of pigmentation, border and surface contour. About 1 year later the patient had noticed an extension of the pigmented macules and plaques; there was also the appearance of nodules of the maxillary gingiva accompanied by swelling. Loosening of teeth as a result of extensive destruction of bone was further noted (Fig. 2).
The histological examination showed a downward streaming in the dermis of the tumor cells and a disintegration and ulceration of the epidermis (Fig. 3). An increased number of large round or polygonal cells resembling atypical epithelioid cells were found on the submucosa. The atypical cells had enlarged, pleomorphic nuclei with prominent and sometimes multiple nucleoli. Mitoses were observed at various tissue levels (Fig. 4). Abundant pigmented melanin was present in the tumor cells (Fig. 5). Many cells had fine, dusty melanin particles. The tumor cells showed great variations in size. Immunohistochemical staining, with S100 protein and HMB45 antibodies, stained many of the spindleshaped cells, indicating that they were melanocytic cells. An inflammatory infiltrate of lymphocytes was seen in a band beneath the invading tumor cells.