Roche announced on October 28, 2026, the global launch of a new laboratory test intended to help pathologists distinguish malignant mesothelioma from benign tissue changes and certain other cancers.
The test, called VENTANA BAP1 (SP527), detects a molecular feature that can help doctors evaluate tissue samples when mesothelioma is suspected.
The development is relevant because diagnosing mesothelioma can be difficult, particularly when the available tissue sample is small or when the findings resemble another cancer or a noncancerous condition.
The new test may provide another standardized laboratory tool, but it does not replace a biopsy, specialist pathology review, or other diagnostic procedures.
Why mesothelioma can be difficult to diagnose
Mesothelioma develops in the thin membranes surrounding organs, most often in the lining around the lungs.
Symptoms and imaging findings may resemble more common illnesses. Even after a biopsy, distinguishing mesothelioma from other cancers or reactive tissue changes can require additional laboratory testing.
The National Cancer Institute describes a diagnostic process that can include imaging, biopsy, examination of fluid or tissue, and immunohistochemistry. Immunohistochemistry uses specialized antibodies to identify proteins in tissue samples. The pattern of these markers can help pathologists distinguish one type of cell or disease from another.
H&S provides additional background in How Mesothelioma Is Diagnosed.
What does the BAP1 test measure?
BAP1 is a protein involved in regulating important cellular functions. In some mesotheliomas, tumor cells lose detectable BAP1 protein expression within their nuclei.
That loss can be useful because it is strongly associated with malignancy in a properly identified mesothelial cell population. The new Roche assay uses automated immunohistochemistry to detect loss of nuclear BAP1 expression.
Roche says the assay can be used alongside other pathology markers to help distinguish mesothelioma from benign mesothelial changes and cancers that may appear similar under the microscope. The company also emphasizes preserving limited tissue samples for additional testing when needed.
Does a normal BAP1 result rule out mesothelioma?
No. A retained BAP1 staining pattern does not exclude mesothelioma.
Not every mesothelioma loses BAP1 expression. Independent research has found BAP1 loss to be highly specific for malignancy when evaluating mesothelial proliferations, but the sensitivity of the marker varies across patients and tumor types.
A 2022 study examining 84 pleural mesotheliomas found that BAP1 loss alone identified approximately 54% of cases. Combining BAP1 with other markers substantially improved sensitivity.
Those results concern BAP1 testing generally, not a separate clinical-validation study of Roche's newly launched SP527 assay.
For a patient, the important point is that pathologists interpret BAP1 results alongside the appearance of the cells, other laboratory markers, imaging, and clinical information. No single result should be considered independently of the full diagnostic evaluation.
Is this a new screening test for asbestos exposure?
No.
The VENTANA BAP1 assay examines tissue samples. It is not a blood test designed to screen people who may have been exposed to asbestos.
It also does not establish whether a particular person's cancer was caused by asbestos or identify where exposure occurred.
BAP1 immunohistochemistry should not be confused with hereditary genetic testing for BAP1-related cancer predisposition. Those are different evaluations.
Has the FDA approved this test?
Roche states that the assay is registered as a Class I in-vitro diagnostic device with the U.S. Food and Drug Administration and has received European IVDR Class C approval.
FDA establishment registration and device listing are not the same as FDA approval or clearance. Accordingly, the October 28 announcement should not be described as a new FDA approval of the assay.
Will the test improve treatment outcomes?
That has not been established.
Roche's October 28 announcement concerns a diagnostic product launch, not a clinical trial demonstrating improved survival or better treatment outcomes.
A more confident diagnosis can be important when doctors are developing a treatment plan, but it would be inappropriate to claim that this product has already demonstrated better patient outcomes.
Readers can continue with H&S information about Mesothelioma Treatment Options.
What should patients ask their doctors?
Patients undergoing evaluation for suspected mesothelioma may wish to ask whether their tissue has been reviewed by a pathologist experienced in mesothelioma, whether BAP1 or other immunohistochemical markers were used, and whether the available findings are sufficient to establish the diagnosis.
If there is uncertainty, patients can ask whether additional pathology review, further testing, or a specialist second opinion would be useful. H&S also provides information about Finding a Mesothelioma Specialist.
For someone who has already received a diagnosis, the launch does not necessarily mean that new testing is required. That decision depends on the original pathology findings and the treating team's assessment.
Why an accurate diagnosis matters
Mesothelioma is uncommon, and treatment decisions depend on the precise diagnosis, disease location, histologic subtype, stage, and the patient's overall circumstances.
Improving the tools available to specialist pathologists is therefore a meaningful area of medical development.
The October 28 Roche announcement represents a new commercial diagnostic offering based on an established molecular marker. It should not be confused with the discovery of a new diagnostic principle or evidence of a cure.
Patients should continue to rely on qualified medical professionals for diagnosis and treatment decisions.
Original sources
- Roche — October 28, 2026 announcement
- Peer-reviewed research — diagnostic capacity of BAP1 and MTAP in mesothelioma
- National Cancer Institute — malignant mesothelioma information
- FDA — device registration and listing
Medical information notice: Humpleby & Strauss, P.C. is a law firm, not a medical provider. This article is intended for educational purposes and does not constitute medical advice. Diagnostic testing and treatment decisions should be discussed with qualified medical professionals familiar with the patient's circumstances. Editorial standards.