Clear cell variant of oral squamous cell carcinoma: case report and review

The clear cell variant of Oral Squamous Cell Carcinoma (OSCC) is an uncommon histological variant. Kuo first discovered it in the skin, and Frazier et al. found it in the oral cavity. We know of only nine cases of clear cell variant of OSCC reported in the literature till now. The present case is in a 60-year-old male patient with an ulcer on the left posterolateral border of the tongue. The patient had a history of chewing tobacco for 22 years. Clinical examination showed features of malignant ulcer associated with pain and discomfort. Histopathological examination revealed sheets and islands of atypical epithelial cells with clear cytoplasm, nuclear and cellular pleomorphism, and few keratin pearls in the connective tissue suggesting OSCC. Various special stains were performed to identify clear cells. Periodic Acid Schiff-Diastase (PAS-D) and Mucicarmine stains showed positive and negative reactions in clear cells, respectively. Immunohistochemical (IHC) analysis for cytokeratin (AE1/AE3) showed diffuse positivity in clear cells and other epithelial cells. Based on special stains and IHC markers, we confirmed the diagnosis as a clear cell variant of OSCC. This variant is rare and presents diagnostic challenges. It is said to be aggressive in nature. More such cases should be reported to understand its biological behavior and prognosis.