Intraosseous mandibular clear cell odontogenic carcinoma with predominant small round blue cells: a potential...

Clear cell odontogenic carcinoma (CCOC) is a rare malignancy of the jaw, presenting significant diagnostic challenges. This report aims to highlight the complexities associated with biopsy-based diagnoses of oral and maxillofacial lesions, as demonstrated in a case of intraosseous mandibular CCOC initially suggestive of Ewing's sarcoma due to its presentation with small round blue cells.

The patient, a 37-year-old male, presented with a mandibular lesion that on incisional biopsy was suggestive of Ewing's sarcoma. Subsequent, comprehensive histologic evaluation after definitive resection via mandibulectomy revealed a CCOC, characterized by a biphasic pattern of clear and basaloid cells. Histological examination confirmed the presence of glycogen-rich clear cells, supported by periodic acid-Schiff (PAS) staining and confirmed by PAS diastase staining, which demonstrated glycogen digestion. Immunohistochemistry was positive for AE1/AE3, p40, and p63, while negative for c-kit and CD34, confirming CCOC and excluding other malignancies such as Ewing's sarcoma, which would have been treated with neoadjuvant chemotherapy instead of primary surgical treatment as in CCOC.

This case highlights the essential need for thorough histopathological evaluation and the value of a second opinion via additional histologic consultation, particularly due to the diagnostic challenges of heterogeneous lesions in the oral and maxillofacial region.