A biologic subset of breast carcinoma defined by high expression of genes characteristic of luminal epithelial cells, including estrogen receptor (ER), estrogen regulated protein LIV-1, and the transcription factors hepatocyte nuclear factor 3, HNF3A, XBP1, and GATA 3. This subtype of breast cancer is associated with a good prognosis. The disease is Monarch Disease Ontology identifier MONDO_0021116 (luminal A breast carcinoma). Also known as: Luminal A, Luminal A breast cancer, Luminal A breast carcinoma, Luminal A estrogen receptor positive subtype of breast carcinoma, Luminal A oestrogen receptor positive subtype of breast carcinoma, Luminal A subtype of breast carcinoma.