However, despite its high sensitivity, CD99 is not entirely specific, as it is also expressed in a wide range of malignancies, including small round blue cell tumors like Ewing sarcoma, desmoplastic small round cell tumors (DSRCT), CIC-rearranged sarcomas, and BCOR-altered neoplasms. The gene discussed is CD99; the disease is desmoplastic small round cell tumor.