Notably, we discovered that HRD tumors were highly enriched in immunogenic epithelial cells, FGFR1+PDGFRβ+ myCAFs, M1 macrophages, tumor reactive CD8+ T cells, and CD4+ Tregs, while HRP tumors were highly enriched in HDAC1‐expressing epithelial cells, indolent CAFs, M2 macrophages, and bystander CD4+/CD8+ T cells. The gene discussed is HDAC1; the disease is hypoparathyroidism-retardation-dysmorphism syndrome.