Here, we demonstrate that CCND1 mutations are of very low frequency across the vast majority of cancer types (0.5%, 151 of 29,432 cases), but are predominantly enriched in endometrial endometrioid carcinomas in both the primary and metastatic settings (6.5%, 30 of 458 cases). Here, CCND1 is linked to endometrial endometrioid carcinoma.