Calretinin

Calretinin  (CAL6). a member of the family of so-called EF-hand proteins that also includes S-100 proteins, is a 29 kDa calcium binding protein that is expressed in central and peripheral nervous system and in many normal and pathological tissues.

Outside the nervous system, calretinin is reported to be expressed in a range of cell types including mesothelial cells, steroid producing cell, (eg adrenal cortical cells, Leydig cells, ovarian theca interna cells as well as Sertoli cells, some neuroendocrine cells, eccrine sweat glands) and other cell types.

Image: Calretinin staining of human mesotheliom. Note cytoplasmic staining of malignant cells. Paraffin section.

The presence of calretinin is reported to be a useful marker primarily for differentiating malignant mesothelioma from carcinomas. Other reports indicate the detection of calretinin is helpful for the differential characterization of ovarian stroma tumors. Calretinin-positive cells have also been reported in the convoluted tubules of kidney with some antibodies.