IGHA1 and breast cancer: IgA1 was found to be present in both the cytoplasm and plasma membrane of 35 out of 36 individual breast cancer tumours The percentage and intensity of staining correlated to some extent with the staining intensity patterns of HPA and GOD-2C4 indicating, as expected, that IgA1 is not the only protein that carries the Tn antigen in the tumour.