Changes in keratin expression during metastatic progression of breast cancer: impact on the detection of circulating tumor cells.

Circulating tumor cells (CTC) might function as early markers for breast cancer metastasis or monitoring therapy efficacy. Enrichment and identification of CTCs are based on epithelial markers that might be modulated during epithelial-mesenchymal transition. Little is known about the expression of keratins in CTCs and whether all CTCs can be detected with antibodies directed against a limited panel of keratins.