Most dMMR breast cancers were invasive ductal carcinomas of no special type (79%) and encompassed 21 (28%) Luminal A-like, 44 (59%) Luminal B-like, 1 (1%) HER2-type, and 9 (12%) TNBCs (Figure 2; Table 3). The gene discussed is ERBB2; the disease is invasive ductal breast carcinoma.