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 scrotum has been reported. We report here a case of pigmented SCC that arose primarily in the scrotum of a 70-year-old man. Light microscopically, this tumour exhibited the typical features of a pigmented SCC, including not only keratinization and intercellular bridges but also colonization by plump dendritic melanocytes with marked pigmentation. These features were clearly confirmed by immunohistochemistry, including strong positivity of tumour cells for high-molecular-weight cytokeratin and of colonizing melanocytes for HMB-45. The tumour was associated with a lentiginous lesion and partly involved it. Melanocytes entrapped from the lentigo might therefore have been activated during enlargement of this tumour, resulting in melanocyte colonization. Fourteen cases of pigmented SCC, including ours, are clinicopathologically reviewed.