Pigmented cutaneous squamous cell carcinoma

Squamous cell carcinoma is an extremely common cutaneous neoplasm, with an incidence second only to basal cell carcinoma and steadily rising, and specimens regularly crossing the reporting pathologist’s bench. Cutaneous pigmented squamous cell carcinoma is a relatively uncommon and perhaps under-recognized pathological variant of squamous cell carcinoma. Florid examples causing clinically evident pigmented lesions are quite rare, with less than 30 cases of cutaneous pigmented squamous cell carcinoma reported in the English literature to date. The pathophysiology of this entity is unknown, and literature addressing this is limited. The diagnosis of cutaneous pigmented squamous cell carcinoma is an important one, as it may be a source of confusion for both clinicians and pathologists because it can be mistaken for other entities including malignant melanoma. In this paper we report a case of cutaneous pigmented squamous cell carcinoma and discuss its clinical and histopathologic features, underlying pathophysiology and important differential diagnoses.