B72.3 (TAG-72)

B72.3 is a monoclonal antibody used in immunohistochemistry (IHC), a laboratory staining technique applied to tissue biopsies, that detects Tumor-Associated Glycoprotein-72 (TAG-72). Pathologists use it to help distinguish adenocarcinoma (a type of lung or other cancer) from mesothelioma, because adenocarcinomas typically stain positive for B72.3 while mesotheliomas typically do not.

Origin

The B72.3 antibody was developed in the early 1980s by researchers at the U.S. National Cancer Institute (Colcher, Schlom, and colleagues), raised against a membrane-enriched fraction of human breast carcinoma. It recognizes TAG-72, a high-molecular-weight mucin-like glycoprotein expressed by many adenocarcinomas.

Significance in Asbestos Context

When a patient has a pleural biopsy for suspected mesothelioma, pathologists rarely rely on appearance alone. They run a panel of immunohistochemical stains to tell mesothelioma apart from metastatic adenocarcinoma (especially lung adenocarcinoma, which can also be asbestos-related but is treated differently). B72.3 is one of the "carcinoma markers" in that panel: a positive stain points toward adenocarcinoma, while a negative stain supports mesothelioma. The accuracy of this distinction matters enormously, because the diagnosis on the pathology report, mesothelioma versus lung cancer versus another cancer, determines treatment, prognosis, and which legal claims and trust funds a patient may access.

Example Sentence

The pathologist's report noted that the tumor cells were negative for B72.3, CEA, and Ber-EP4 but positive for calretinin and WT-1, supporting a diagnosis of epithelioid mesothelioma rather than metastatic adenocarcinoma.

Related Terms

Immunohistochemistry (IHC), Calretinin, Ber-EP4, CEA, Mesothelioma, Adenocarcinoma

Notes

• Ask your pathologist or oncologist for a copy of the full pathology report, including the IHC panel results. The specific stains used and whether each was positive or negative are critical to confirming a mesothelioma diagnosis.
• If only a small panel of stains was run, request a second opinion from a mesothelioma-experienced pathology center (such as the U.S.–Canadian Mesothelioma Reference Panel); diagnostic accuracy directly affects treatment and legal eligibility.
• B72.3 is not a blood test in this context. It is applied to biopsy tissue. Be cautious of any summary that describes it as a serum marker for asbestos disease.
• Preserve all biopsy slides and paraffin blocks; defense experts in litigation may request to re-stain them, and your own experts may need them for confirmatory testing.