Cytokeratin 19 (KRT19) is a cytoplasmic intermediate filament protein, which is responsible for structural rigidity and multipurpose scaffolds. In several cancers, KRT19 is overexpressed and may play a crucial role in tumorigenic transformation. The KRT19 gene encodes cytokeratin 19, an element of the cytoskeleton whose expression is frequently altered in renal cell carcinoma (RCC).KRT19 was identified as one of the key biomarkers for distinguishing cholangiocarcinoma (CCA) and hepatocellular carcinoma. Expression of KRT19 was specifically high in breast cancers and significantly correlated with their invasiveness. Moreover, knockdown of KRT19 led to increased proliferation, migration, invasion, drug resistance, and sphere formation in breast cancer cells via an upregulated NOTCH signaling pathway.