Clear Cell Squamous Cell Carcinoma in Buccal Mucosa: A Rare Variant with Review of Literature

A BSTRACT Oral squamous cell carcinoma (OSCC) with prominent clear-cell differentiation is a rare entity with less understood etiopathogenesis and clinical behavior. There are several histological variants of squamous cell carcinoma with varied prognosis and causing diagnostic dilemma. Awareness of this entity will help in accurate diagnosis and proper management of the case. We present one such case of ulcer-proliferative lesion over the right buccal mucosa in a 38-year-old male patient. Microscopy revealed squamous cell carcinoma with more than 80 percent cells showing clear cell morphology. The clear cells were negative for mucicarmine, periodic acid Schiff (PAS), periodic acid Schiff-diastase (PAS-D), and alcian blue (AB). Immunohistochemistry showed the tumor cells were immuno-positive for CK5/6 and Ki-67, but S100 was immuno-negative, suggesting a diagnosis of Clear cell squamous cell carcinoma. We reviewed the literature to understand the clinical behavior of this rare entity. Early identification of high-risk variant can allow rapid therapeutic intervention with better clinical outcome.