Carcinoma de células escamosas pigmentado. Descripción de un caso y revisión de la literatura

The majority of pigmented cutaneous tumours are melanocytic, although there are other epithelial entities that are clinically similar, such as pigmented squamous cell carcinoma. We report the case of a 78 year old man who presented with a pigmented lesion on the left temple, clinically and dermoscopically suspicious of melanoma. After complete excision the lesion was seen to have infiltrating atypical squamous proliferation, with numerous mitoses and several associated stromal melanophages. Immunohistochemical studies revealed a dendritic melanocytic population, arranged in an intratumoral homogeneous reticular pattern, without mass or sheet formation or significant cytological atypia. These features rule out a malignant biphasic squamo-melanocytic lesion, based on the absence of malignant criteria in the melanocytic component. Pigmented squamous cell carcinoma is a rare variant of cutaneous squamous cell carcinoma but should be considered in the differential diagnosis of pigmented atypical cutaneous lesions, especially of melanoma and squamo-melanocytic tumour.