Calretinin is a binding protein involved in calcium signalling. The CALB2 gene encodes this protein, which is essential for cells to work. Certain neurons in the nervous system express calretinin. It is also found in specialized cells, such as Leydig cells. These cells produce testosterone. The calretinin protein is present in several other locations, including hair follicles. It has become a valuable biomarker for specific illnesses. These include Hirschsprung disease and malignant mesothelioma. Pathologists use immunohistochemistry to tell different forms of cancer and cell types apart. Calretinin is one of several immunohistochemical markers used to diagnose malignant mesothelioma. Cytokeratin (CK)-19 is a type I cytokeratin, has been found to be a reliable marker of epithelial differentiation. The intense expression of CK-19 is useful for identification of odontogenic epithelial components, thus suggesting their potential for proliferation to form epithelial odontogenic cysts and tumour’s.