Calretinin

Calretinin is a 29 kDa calcium‑binding protein that shows combined nuclear and cytoplasmic staining on IHC and is used primarily to support mesothelial or sex‑cord stromal lineage. It is strongly positive in pleural and peritoneal mesotheliomas while negative in lung adenocarcinomas, making it a key component of mesothelioma diagnostic IHC panels. Calretinin also assists in evaluating Hirschsprung disease by highlighting normal mucosal innervation, and helps distinguish adrenal cortical lesions (positive) from pheochromocytoma (negative). Additional uses include confirming sex‑cord stromal tumours and contributing to panels for mesonephric carcinoma and STK11‑associated adnexal tumours (1).

Recommended Controls

Criteria for acceptable staining is strong cytoplasmic and nuclear staining. Appendix will demonstrate both negative (columnar epithelial cells and smooth muscle cells) and strong distinct positive cytoplasmic and nuclear staining (peripheral nerves, ganglions, axons and macrophages).

Expected staining pattern

Appendix ganglion cells

Mesothelioma

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.