Doctors use several steps to evaluate possible mesothelioma. The process typically begins with a history and physical examination, followed by imaging. Fluid tests may provide useful information, but a biopsy—removing tissue for examination by a pathologist—is generally needed to confirm mesothelioma and identify its cell type.
Key takeaways
- Symptoms and imaging can raise suspicion but do not by themselves confirm mesothelioma.
- A biopsy supplies tissue that a pathologist can examine under a microscope and test with special stains.
- Mesothelioma may be difficult to distinguish from lung cancer or other diseases.
- A second pathology review or consultation at an experienced center may be helpful.
- Diagnostic and staging results guide treatment planning.
Medical and exposure history
A clinician will ask about symptoms, when they began, medical history and possible exposures. Relevant work may include construction, insulation, maritime, shipyard, industrial, automotive, railroad and power-generation jobs. Military service, renovation work and household contact with an exposed worker may also matter.
Not remembering an exposure does not rule out mesothelioma. Conversely, prior exposure does not mean that current symptoms are cancer.
Imaging tests
Imaging can identify fluid, thickening, masses and areas that may require further evaluation.
Chest X-ray
An X-ray can show structures in the chest and may reveal fluid or other abnormalities. It is less detailed than CT.
CT scan
Computed tomography produces detailed cross-sectional images. Contrast material may be used when medically appropriate. CT can help assess the chest or abdomen, guide procedures and evaluate the extent of disease.
PET and MRI
Doctors may use positron emission tomography or magnetic resonance imaging in selected situations to assess possible spread or involvement of nearby structures. The tests required depend on the individual case.
Fluid sampling
If fluid has accumulated around a lung or in the abdomen, a clinician may remove some with a needle. Laboratory examination can look for abnormal cells and may relieve symptoms. However, a fluid sample may not provide enough information to rule mesothelioma in or out.
Biopsy and pathology
A biopsy removes cells or tissue for examination. The approach depends on tumor location, imaging, health and the amount of tissue needed. Procedures may include needle biopsy or a procedure using a scope to inspect the chest or abdomen and collect tissue.
A pathologist examines the tissue’s appearance and may use immunohistochemistry—special laboratory stains that help identify proteins in the cells. This helps distinguish mesothelioma from cancers that have spread from another organ.
Pathology may identify one of three broad cell patterns:
- Epithelioid
- Sarcomatoid
- Biphasic, containing both patterns
Cell type is one factor considered in prognosis and treatment planning.
Staging after diagnosis
Staging describes the extent of cancer. For pleural mesothelioma, doctors consider the primary tumor, lymph nodes and distant spread. Imaging and sometimes procedures provide the information needed. Other forms of mesothelioma may be described using different clinical approaches.
Read about mesothelioma stages
Getting a second opinion
Mesothelioma is uncommon and can be challenging to diagnose. A second opinion may confirm the diagnosis, suggest additional testing or provide another treatment perspective. Ask how to obtain:
- Pathology report and slides or digital pathology files
- Imaging reports and image discs or electronic transfers
- Procedure and operative reports
- Laboratory results
- Current medication list and medical summary
Insurance coverage and referral requirements vary, so confirm them in advance when possible.
Questions to ask after diagnosis
- What exact type and cell pattern did the pathology show?
- Has a pathologist experienced with mesothelioma reviewed the tissue?
- What stage is recorded, and how was it determined?
- Are additional tests needed before choosing treatment?
- Should a multidisciplinary tumor board review the case?
- Are biomarker or molecular tests relevant?
- Are clinical trials appropriate to consider now?
Sources
- National Cancer Institute. Mesothelioma Diagnosis and Prognosis Updated May 16, 2025.
- National Cancer Institute. Stages of Mesothelioma Updated May 16, 2025.
- National Cancer Institute. Malignant Mesothelioma Treatment—Health Professional Version.
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