Pigmented squamous cell carcinoma of the scrotum associated with a lentigo

Only 13 cases of pigmented squamous cell carcinoma (SCC) have been reported in the English language literature, with most frequent development in the oral cavity and conjunctiva. However, no case of pigmented SCC of the scrot um has been reported. We report here a case of pigmented SCC that arose pri marily in the scrotum of a 70-year-old man. Light microscopically, this tum our exhibited the typical features of a pigmented SCC, including not only k eratinization and intercellular bridges but also colonization by plump dend ritic melanocytes with marked pigmentation. These features were clearly con firmed by immunohistochemistry, including strong positivity of tumour cells for high-molecular-weight cytokeratin and of colonizing melanocytes for HM B-45. The tumour was associated with a lentiginous lesion and partly involv ed it. Melanocytes entrapped from the lentigo might therefore have been act ivated during enlargement of this tumour, resulting in melanocyte colonizat ion. Fourteen cases of pigmented SCC, including ours, are clinicopathologic ally reviewed.