Immunohistochemical studies of mucinous mammary carcinomas and their metastases.

In cancer cells the expression of mucins is variable in amount and cellular localization. Alteration in glycosylation occurs and leads to the appearance of novel structures. The aim of this study was to investigate the expression of epitopes known as CA19-9, CA50, CA242, MUC1, MUC1-Core and Thomsen-Friedenreich (TF) in mucinous carcinomas. The formalin-fixed and paraffin-embedded tissue samples of the breast (n=29) and their metastases in axillary lymph nodes (n=6) were analysed using immunohistochemical methods. The mucinous breast tumours expressed MUC1, MUC1-Core and TF, while CA19-9, CA50 and CA242 showed a negative staining reaction. The examined metastases showed similar expression patterns as the corresponding primary tumours. In the case of an unknown metastatic primary tumour, such immunohistochemical analysis in axillary lymph nodes might be helpful. A positive reaction of CA19-9, CA50 and CA242 might suggest the presence of a gastrointestinal tumour, especially a pancreatic carcinoma, whereas positive findings of MUC1, MUC1-Core and TF could indicate the presence of a mucinous mammary carcinoma.