Germline or somatic BRG1-LOF mutations are characteristic and diagnostic features in nearly 100% of highly aggressive and poorly differentiated tumors with a rhabdoid morphology, such as small cell carcinoma of the ovary hypercalcemic type (SCCOHT) and SMARCA4-deficient thoracic sarcomas (SMARCA4-DTS) [6,7]. Here, SMARCA4 is linked to ovarian small cell carcinoma.