Pigmented squamous cell carcinoma with dendritic melanocytes

A 79-year-old man presented with a pigmented nodule on the right ear which, on epiluminescence microscopy, demonstrated a diffuse grey-blue colour. Skin biopsy revealed an irregularly acanthotic epidermis with lobular clusters of atypical keratinocytes that projected into the dermis in the pattern of an invasive squamous cell carcinoma. Numerous dendritic melanocytes were present throughout the lesion. Although the close relationship between the highly dendritic intra-epidermal melanocytes and the atypical keratinocytes raised the issue of whether this tumour represented a malignant melanoacanthoma, the authors considered the lesion to be better classified as an unusual variant of pigmented squamous cell carcinoma.