Medullary carcinoma cases showed characteristically high lymphocyte infiltration and high CD8+ area (mean 24.0%, median 19.7%, pooled intrapatient SD: 1.7%), compared to ductal adenocarcinoma (mean 8.8%, median 5.9%, pooled intrapatient SD: 1.2%). Here, CD8A is linked to invasive ductal breast carcinoma.