Immunohistochemistry

Immunohistochemistry (IHC) is a laboratory technique that uses antibodies tagged with a colored stain to detect specific proteins inside cells on a tissue slide. Pathologists use it to tell different cancers apart when cells look similar under the microscope. For mesothelioma, IHC is essential because mesothelioma cells can closely resemble lung adenocarcinoma, reactive mesothelial cells, and other tumors that have spread to the lining of the lung or abdomen.

Origin

The technique was developed by Albert Coons in 1941, when he first used fluorescent-labeled antibodies to detect bacterial antigens in tissue. The name combines 'immuno-' (antibodies), 'histo-' (Greek for tissue), and 'chemistry,' reflecting its core idea: using the immune system's targeting ability to chemically mark proteins in tissue.

Significance in Asbestos Context

A confident mesothelioma diagnosis almost always rests on an IHC panel performed on biopsy tissue. Because no single stain is perfect, pathologists run a panel of markers, typically including at least two 'positive' mesothelial markers (such as calretinin, WT-1, CK5/6, or D2-40/podoplanin) and at least two 'negative' markers that would suggest a different cancer (such as MOC-31, BerEP4, claudin-4, CEA, or TTF-1 for lung adenocarcinoma). Newer markers like BAP1 loss and MTAP loss help distinguish malignant mesothelioma from benign reactive changes. The strength and pattern of these stains is what allows a pathologist to commit to the diagnosis, and the IHC report is one of the most important documents in both your medical record and any legal claim. Defense experts will scrutinize it closely, so the panel should be thorough and follow current guidelines (such as those from the International Mesothelioma Interest Group).

Example Sentence

The pathologist confirmed epithelioid mesothelioma after immunohistochemistry showed strong calretinin and WT-1 staining, negative MOC-31 and claudin-4, and loss of BAP1.

Related Terms

Mesothelioma, BAP1, Calretinin, Pathology, Biopsy, Epithelioid Mesothelioma

Notes

• Request a copy of your full pathology report, including the complete IHC panel with each marker and whether it was positive or negative, not just the final diagnosis line.
• If your panel was limited (only one or two markers), ask whether additional staining, including BAP1 and MTAP, can be performed on the existing tissue block; this is often possible without a new biopsy.
• Ask your oncologist whether a second pathology opinion at a mesothelioma specialty center (such as a National Cancer Institute-designated center) is warranted, since mesothelioma is frequently misdiagnosed on initial review.
• Make sure the paraffin-embedded tissue blocks and unstained slides are preserved; they may be needed for additional testing, expert review, or as evidence in a legal claim.