Oral mucosa malignant melanoma in situ with involvement of the perioral skin.

A 66-year-old Japanese woman had a pigmented macule spreading from the internal aspect of the cheek to the vermilion border and perioral skin. Histology was that of in situ malignant melanoma. This case appears to be unique as it implies a longer period of radial growth than is usually observed in malignant melanoma of the oral mucosa.