MOC-31

MOC-31 is an antibody used in pathology laboratories to detect a protein called EpCAM (epithelial cell adhesion molecule) on the surface of cells. It is one of the most reliable "adenocarcinoma markers" used to help distinguish metastatic carcinoma (especially lung adenocarcinoma) from mesothelioma when a pathologist examines a tissue biopsy or fluid sample. A positive MOC-31 result typically points away from mesothelioma and toward a different type of cancer.

Origin

The MOC-31 antibody was developed in the late 1980s by researchers studying small-cell and non-small-cell lung carcinomas; the name comes from "monoclonal antibody to oat-cell carcinoma" (clone 31). It became a standard immunohistochemistry reagent in the 1990s as pathologists searched for reliable markers to separate mesothelioma from adenocarcinoma involving the pleura.

Significance in Asbestos Context

For patients with suspected mesothelioma, MOC-31 is one of the immunostains pathologists use to make sure the diagnosis is correct. Mesothelioma is almost always MOC-31 negative, while lung, breast, ovarian, and gastrointestinal adenocarcinomas that have spread to the pleura or peritoneum are usually MOC-31 positive. This distinction matters because mesothelioma and metastatic adenocarcinoma can look nearly identical under the microscope, but the treatment, prognosis, and legal claim are very different. If your pathology report mentions MOC-31, the result helps confirm, or rule out, mesothelioma as the source of disease.

Example Sentence

The pathology report noted that the tumor cells were MOC-31 negative and calretinin positive, supporting a diagnosis of epithelioid mesothelioma rather than metastatic lung cancer.

Related Terms

Immunohistochemistry, Calretinin, WT-1, BerEP4, Epithelioid Mesothelioma, Adenocarcinoma

Notes

• Ask your oncologist or pathologist for a copy of the full immunohistochemistry panel. MOC-31 should be interpreted alongside mesothelial markers like calretinin, WT-1, D2-40, and cytokeratin 5/6, not in isolation.
• If your diagnosis is uncertain, request that the slides be sent for a second opinion at a mesothelioma specialty center (such as a National Cancer Institute–designated center); confirmation often depends on the immunostain panel used.
• Preserve all pathology reports, slides, and tissue blocks. These are critical both for guiding treatment and for documenting the diagnosis if you pursue a legal claim.
• A MOC-31 positive result does not rule out asbestos-related disease entirely; asbestos exposure is also linked to lung cancer, which is typically MOC-31 positive.