Desmoplastic Small Round Cell Tumor of Parotid Gland: A Rare Entity With Diagnostic Challenge.

Desmoplastic small round cell tumor (DSRCT) is a rare malignant mesenchymal neoplasm that typically affects young patients and presents as large intraabdominal masses. We report a rare case of parotid gland DSRCT in a 38-year-old man. The tumor cells were large sized and form irregular nests embedded in abundant desmoplastic stroma. Immunohistochemically, the tumor cells were positive for cytokeratin, GATA3, p40, and p63. Working differential diagnosis included squamous cell carcinoma, myoepithelial carcinoma, hyalinizing clear cell carcinoma, NUT (nuclear protein of the testis) carcinoma, and adamantinoma-like Ewing sarcoma. The characteristic morphologic features and presence of EWSR1-WT1 gene fusion are diagnostic of DSRCT. Salivary gland DSRCT is an exceedingly rare entity, with only 6 cases reported in the literature.