Cytokeratin 7/8 （CK7/8） proteins are intermediate filament proteins that play crucial roles in maintaining the structural integrity and function of epithelial cells. CK7, also known as sacolectin, is a type II cytokeratin typically found in glandular epithelia and transitional epithelium, including their associated tumors. CK8 is a type I cytokeratin that pairs with CK7 to form heterodimers, which are essential for the stability and function of the cytoskeleton in epithelial cells. These proteins are widely expressed in various organs and tissues, such as the thyroid, lung, female reproductive organs, upper digestive tract, and head and neck region. In pathology, CK7/8 are valuable markers for distinguishing epithelial tumors and identifying their origins. For example, CK7 is often positive in tumors of the breast, lung, and female reproductive system, while CK8 helps in further characterizing these tumors. Their expression patterns can also provide insights into the differentiation and behavior of tumor cells.