In a study encompassing more than 1,300 cases of breast cancer it was clearly shown that the specific tissue architecture of MUC1-expressing cells has prognostic value: cytoplasmic expression with circumferential membranous MUC1-TM localization was unmistakably associated with a worse prognosis, whereas apical, luminal expression predicted a favorable outcome. Here, MUC1 is linked to breast carcinoma.