Malignant lesion of clear cells: A diagnostic challenge of an unusual presentation mimicking a benign lesion

In the oral cavity, a broad spectrum of differential diagnostics includes lesions composed of clear cells. Under this umbrella, Clear Cell Odontogenic Carcinoma (CCOC) and Hyalinizing Clear Cell Carcinoma (HCCC) are rare malignancies that arise from different histological origins. However, the histology is similar; therefore, differentiation of CCOC and HCCC lesions is difficult and, in some cases, impossible to distinguish morphologically and immunohistochemically. Herein, we report an unusual presentation of a well-defined nodular lesion affecting the maxillary gingiva in a 19-year-old female, which presented clinically as a benign or reaction etiology lesion. Microscopic evaluation showed a tumor composed of cell sheets with clear cytoplasm, separated by septa of fibrous tissue and invading the connective tissue. Tumor cells were positive for p63 and AE1/AE3 and negative for PAX8, smooth muscle actin (AML) and estrogen receptor. The diagnosis was carcinoma with a clear cell pattern, and it was not possible to distinguish between HCCC and CCOC. In this study, clinicopathologic, histologic, and immunohistochemistry features of CCOC and HCCC were discussed due to the challenging histological diagnosis. Radical surgical treatment and rehabilitation of the patient through graft and dental implants were performed. The patient is under follow-up with no signs of recurrence.