Ck-19 expression levels are associated with several key tumor molecular features such as estrogen and progesterone receptor expression in breast cancer, and von Hippel-Lindau gene alterations in kidney tumors, suggesting that altered cellular functions or the differentiation status of neoplastic cells can be as easily influenced by expression levels and filament composition such as Ck-19 (27). This evidence concerns the gene PGR and breast carcinoma.