RB1 and synovial sarcoma: In synovial sarcoma, CDK4 is highly expressed and high CDK4 expression was associated with a poor prognosis.38 A genetic disruption of CDKN2A is frequently detected in malignant peripheral nervous sheath tumors (MPNST) that elicits the de-repression of CCND1 and CCNE1 and could drive the MPNST progression.39 Genomic data highlight that the CDKN2A-CDK4/6-RB1 pathway is affected in more than 25% of sarcomas and represents a key oncogenic driver.13,40