CD99 is reported to be related to immunomodulation, homeostasis, and antitumorigenesis via inhibiting cell migration, especially in osteosarcoma; WT1 was found to exert an antitumor effect in hematological and kidney diseases.[28–32] Given their role in tumorigenesis, some researchers have investigated them in the differential diagnosis of SCST.[33–35] As in granulosa cell tumors, we found value in their identification in pure stromal tumors, especially between LTSP and thecoma. The gene discussed is CD99; the disease is osteosarcoma.