The cytokeratin profile of medullary carcinoma of the breast

Aims: The cytokeratin (CK) phenotype and vimentin expression of 31 medullary carcinomas was studied using commercially available antibodies on archived material, Comparing the phenotype of typical and atypical tumours and the phenotype of metastases, the biological significance of cytokeratin and vimentin expression in medullary carcinomas of the breast was determined, Methods and results: Antibodies to CK4, CK5 and 6, CK7, CK14, CK8 and 18, CK19, CK20 and to vimentin were used. All the typical and atypical medullary carcinomas and the metastases (10 cases) stained negatively for CK4 and positively for CK8-18 (CAM5.2). Almost all the tumours were CK7 and CK19 positive and CK20 negative, Twelve per cent of the tumours contained CK14. Twenty-five per cent of the typical, 43% of the atypical and 30% of the metastatic medullary carcinomas showed CK5-6 positivity. No association between the cytokeratin-vimentin profile of the tumours and axillary node metastases, tumour size or oestrogen receptor status was found but instability of CK expression was demonstrated by comparing the primary tumours with their metastases, Conclusions: Medullary carcinomas of the breast express all the glandular type CKs including CK19 and additionally a proportion of the tumours expresses some of the CKs typical for myoepithelial cells. There was no correlation with prognostic factors.