Primary glycogen-rich clear cell squamous cell carcinoma of the mandibular gingiva.

Clear cell squamous cell carcinoma (CCSCC) is a rare variant of squamous cell carcinoma, first reported by Kuo, who described 6 cases of squamous cell carcinoma of the skin of the head and neck. CCSCC is composed of cells with clear cytoplasm, which Kuo attributed to the accumulation of intracellular fluid and not the presence of glycogen, lipid, or mucin. This case describes a 59-year-old woman who presented with an exophytic, hemorrhagic lesion on the posterior mandibular gingiva of 2 months' duration. Histologic examination revealed dysplastic stratified squamous epithelium showing transition to an infiltrating tumor composed of islands of epithelial cells with clear cytoplasm. The cytoplasm stained positive with periodic acid Schiff but was diastase labile. Mucicarmine stains were negative for intracytoplasmic mucin. This is the first reported case describing primary glycogen-rich CCSCC of the mandibular gingiva.