Differentiation of human breast carcinomas: an immunohistological study of appropriate and inappropriate protein production.

Secretory piece of immunoglobulin A, a product of normal breast tissue, and beta 1 pregnancy-specific glycoprotein, a product of syncytiotrophoblast of placenta, have been demonstrated in breast carcinomas by an indirect immunoperoxidase method. A close relationship has been found between the site of staining within cells and tumour structure for both secretory piece, the appropriate protein, and beta 1 pregnancy-specific glycoprotein, the inappropriate protein. The reaction was at the periphery of cells in areas of tubular differentiation and was diffusely intracytoplasmic in solid groups of tumour cells. The poorly differentiated carcinomas have a low incidence of detection for both antigens but the tumours showing good histological differentiation appear to be functionally heterogeneous with some being negative for both proteins, some staining for the appropriate secretory piece of immunoglobulin A and the inappropriate beta 1 pregnancy-specific glycoprotein and only one out of 12 producing the appropriate protein alone.