Among these immunoreactive autoantigens, there are 2 proteins; in particular, Zuotin-related factor 1 (ZRF1) and R motif-containing protein 1 (KRR1) (clones KY-MBC 29-88-1 and KY-MBC 18-53-1) were identified during the screening of cDNA library from medullary breast carcinoma. This evidence concerns the gene KRR1 and medullary breast carcinoma.