Signet ring squamous cell carcinoma--the forgotten variant: case report and review of the literature.

Squamous cell carcinoma is one of the commonest skin cancers. In most instances, histological diagnosis is straightforward and does not pose any diagnostic challenge to the handling pathologist. We report a rare case of signet ring squamous cell carcinoma (SRSCC) occurring in an 84-year-old woman who presented with a sore on the upper lip. Excision of the lesion showed signet ring carcinoma within a scar and surface ulceration. Deeper sections showed focal area of squamous differentiation. Although rare, consideration of squamous cell carcinoma as a diagnosis of primary skin tumors with signet ring morphology, especially in the absence of history of adenocarcinoma, may prevent missing rare cases of SRSCCs.