Calretinin is a calcium-binding protein found naturally in the human body. It participates in various cellular functions, including maintaining calcium balance within cells. Its presence in different tissues is relevant in understanding normal biological processes and medical diagnostics.
What is Calretinin and What Does It Do?
Calretinin is a calcium-binding protein with specific structural motifs that enable it to bind calcium ions and modulate intracellular calcium signals. It is predominantly found in neurons of the central and peripheral nervous systems.
It is also observed in various non-neuronal cells, including mesothelial cells and during embryonic development. Its role extends to cellular signaling, regulating calcium ion concentration within the cytoplasm. This influences neuronal excitability and is linked to processes such as cell proliferation, differentiation, and cell death.
Calretinin as a Diagnostic Marker
When a diagnostic report indicates “calretinin positive,” it means the protein has been detected in the cells or tissue examined. This is a significant finding in medical diagnostics, particularly in pathology. It serves as an immunohistochemical marker, a tool that helps pathologists identify specific cell types or distinguish between different conditions.
Immunohistochemistry is the laboratory method used for this detection. Specific antibodies bind to calretinin in tissue or fluid samples, often linked to a fluorescent dye for visualization under a microscope. This aids in differentiating various diseases, especially when symptoms or imaging alone cannot provide a definitive diagnosis.
Key Conditions Where Calretinin Positivity is Significant
Calretinin positivity is a valuable indicator in diagnosing several medical conditions.
Mesothelioma
Calretinin is most recognized for differentiating malignant mesothelioma from other lung cancers, such as adenocarcinoma. Mesothelioma, a cancer affecting the lining of the lungs, often shows strong calretinin expression, unlike adenocarcinomas. Calretinin can identify epithelioid mesothelioma with up to 90% accuracy, though its accuracy is lower for sarcomatoid mesothelioma, around 55%.
Hirschsprung’s Disease
The protein also plays a role in diagnosing Hirschsprung’s disease, a congenital condition characterized by the absence of specific nerve cells in parts of the colon. In normal intestinal biopsies, calretinin stains positive in nerve fibers and ganglion cells. Conversely, in segments of the bowel affected by Hirschsprung’s disease, there is an absence of calretinin-positive nerve fibers, which aids in confirming the diagnosis.
Brain Tumors and Other Applications
Calretinin’s utility extends to classifying certain brain tumors. Antibodies against calretinin can help distinguish between different types of brain tumors, particularly those with neuronal differentiation from those with glial differentiation. While not as broadly expressed in brain tumors as in mesothelioma, its presence can assist in precise tumor classification. Calretinin is also found in some normal cells, including adipocytes, eccrine glands, and steroid-producing cells in the ovaries, testes, and adrenal cortex. It is also expressed in other neoplasms such as sex cord-stromal tumors, adrenal cortical neoplasms, and olfactory neuroblastomas.