Calretinin (CR)

Calretinin is a calcium-binding protein, 29 kDa, member of the family of so-called EF-hand proteins, to which also the S-100 proteins belong. Calretinin is abundantly expressed in neurons. Outside the nervous system, calretinin is found in mesothelial cells, steroid producing cells (adrenal cortical cells, testicular Leydig cells, ovarian theca interna cells), testicular Sertoli cells, rete testis, ovarian surface epithelium, some neuroendocrine cells, breast glands, eccrine sweat glands, hair follicular cells, thymic epithelial cells, endometrial stromal cells, and fat cells. In calretinin positive cells, the protein is generally found in both the cytoplasm and nuclei.Calretinin is also considered an important diagnostic aid in the differential diagnosis of cystic and solid ameloblastic tumors.