Salivary Hyalinizing Clear Cell Carcinoma: Report of a Genetically Confirmed Pediatric Case and Review of the Literature

Hyalinizing clear cell carcinoma (HCCC) is a rare but well-recognized low-grade salivary gland malignancy. In addition to being amorphologically distinct neoplasmwith cords and nests of predominantly clear cells in hyalinized fibrous stroma, it harbors a characteristic EWSR1 gene rearrangement that can be readily exploited as a diagnostic marker to help distinguish it from other salivary gland tumors with overlapping histomorphology.We herein report a pediatric case of salivary HCCC arising in the oral cavity of an 11-year-old girl. The tumor cells containedmoderate amounts of eosinophilic to clear cytoplasm and hyperchromatic nuclei. The stroma was notable for a biphasic spatial arrangement alternating between fibrocellular regions and hyalinized basement membrane-like areas immediately adjacent to tumor cell nests. By immunohistochemistry, the tumor was positive for p40 and negative for SOX10, S100 protein, and smooth muscle actin. Fluorescence in situ hybridization was positive for an EWSR1 chromosomal rearrangement. This is the first reported,molecularly confirmed pediatric case of HCCC. It further expands the diagnostic age range of HCCC to include the pediatric population and highlights the potential risk of misdiagnosis.