Decoding the Rarity: A Unique Case of Clear-Cell Variant of Oral Squamous Cell Carcinoma

The clear-cell variant of oral squamous cell carcinoma is an extremely rare histological variant and an incompletely understood entity. Clear cell appearance in squamous cell carcinoma may be attributed to hydropic degeneration of neoplastic cells. We report a case of a 32-year-old male patient who presented with an ulceroproliferative growth in the left maxillary posterior region on the hard palate and gingiva, obliterating the buccal vestibule. Histopathologic examination revealed thick anastomosing strands of round to ovoid neoplastic cells with predominantly clear cytoplasm and marked cellular and nuclear pleomorphism infiltrating into the fibro-cellular connective tissue stroma. Special staining and immunohistochemistry (IHC) were performed to rule out the differentials of clear-cell variants of different sites such as salivary gland, odontogenic origin, and metastatic tumors. The clear cells were negative for periodic acid Schiff (PAS) and mucicarmine. The malignant clear cells showed positive reactions with IHC markers pan-cytokeratin and P63 and yielded negative results for S100 and CD10, confirming the diagnosis as a clear-cell variant of oral squamous cell carcinoma. We emphasize the importance of prompt and comprehensive diagnostic work-up to identify this rare, aggressive, and possibly fatal neoplasm.