Calretinin

Calretinin is a calcium-binding protein that pathologists detect in tissue samples to help confirm mesothelioma. Mesothelial cells typically stain positive for calretinin, while most lung adenocarcinomas and many other cancers do not. It is one of several stains used together to distinguish mesothelioma from cancers that can look similar under the microscope.

Origin

Calretinin was first described in 1987 by Rogers and colleagues, who isolated it from chicken retina, hence the name combining "calcium" and "retina." It was later recognized as a reliable marker of mesothelial differentiation in the 1990s and became a standard tool in mesothelioma pathology.

Significance in Asbestos Context

For a patient with suspected mesothelioma, a calretinin stain on the biopsy is often one of the key tests that confirms the diagnosis. Pathologists use it alongside other markers (such as WT-1, cytokeratin 5/6, and D2-40) and "negative" markers (such as TTF-1, CEA, and Claudin-4) to distinguish mesothelioma from lung adenocarcinoma, breast cancer spread, or other tumors that can mimic it. Because mesothelioma is the disease most strongly tied to asbestos exposure, a clear, well-documented immunohistochemistry panel, including calretinin, is often central to both treatment planning and any legal claim, since defendants frequently challenge whether the cancer is truly mesothelioma.

Example Sentence

Her biopsy report noted strong nuclear and cytoplasmic calretinin staining, supporting the diagnosis of epithelioid mesothelioma rather than metastatic lung cancer.

Related Terms

Mesothelioma, Immunohistochemistry, WT-1, Cytokeratin 5/6, D2-40, Epithelioid Mesothelioma

Notes

• Ask your oncologist or pathologist for a copy of the full immunohistochemistry panel, not just the diagnosis line, and confirm that calretinin and at least one or two other mesothelial markers were positive.
• Calretinin is not specific to mesothelioma on its own; it can appear in some other tumors, which is why diagnosis relies on a panel of markers plus clinical and imaging findings.
• If the diagnosis is uncertain or the panel is limited, request a second opinion from a mesothelioma specialty center (such as a National Cancer Institute–designated center); accurate subtyping affects both treatment and any legal claim.
• Preserve the original pathology slides and tissue blocks. These may be needed later for additional staining, molecular testing (e.g., BAP1, MTAP), or expert review in litigation.