Medullary breast carcinoma (MBC) despite anaplastic features and high grade has a good prognosis that can be related to prominent lymphocytic infiltration. We analyzed the frequency of antibody response toward 41 SEREX (serological recombinant expression cloning)-defined MBC antigens in sera of allogeneic MBC patients using serological plaque-spot assay and examined the mRNA expression profile of some antigens in MBC tissues. This preliminary study allowed us to select 18 autoantigens as potential MBC-associated antigens. Further studies in large cohorts of breast cancer patients will be performed for their evaluation as targets for cancer diagnostics or therapy.