ARID1B and uterine corpus sarcoma: However, ARID1B loss has not yet been reported in pediatric and young adult undifferentiated malignancies, such as SCCOHT and SMARCA4-deficient uterine sarcoma (SDUS), or malignant rhabdoid tumors of the kidney (MRT), and atypical teratoid rhabdoid tumor (ATRT).