Mesothelioma Diagnosis

Expert Fact Checked

This page was medically reviewed by James Stevenson, M.D. on February 22, 2019. For information on our content creation and review process read our editorial guidelines. If you notice an error or have comments or questions on our content please contact us.

James Stevenson, M.D. Thoracic Medical Oncologist

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Doctors confirm a mesothelioma diagnosis with a biopsy. After displaying mesothelioma symptoms, a doctor will conduct a physical exam. They then may order X-rays, CT scans and blood tests to identify mesothelioma. But, a biopsy is the only way to definitively confirm a mesothelioma diagnosis.

01. Diagnostic Process

How Is Mesothelioma Diagnosed?

When a patient presents symptoms of mesothelioma, doctors will conduct a physical exam and look at the patient’s medical history to rule out more common diseases and conditions. If known asbestos exposure has occurred, patients should inform their doctor at this time. The only way to accurately confirm a mesothelioma diagnosis is through a biopsy.

Challenges to Mesothelioma Diagnosis

  • Latency period: Mesothelioma symptoms often present 10 – 50 years after asbestos exposure. This extended time period between asbestos exposure and symptoms leads to delayed diagnosis.
  • Nonspecific symptoms: Common signs and symptoms of mesothelioma are often mistaken for other illnesses, such as the flu, pneumonia and irritable bowel syndrome.
  • Limited knowledge of disease: Due to the rarity of mesothelioma, only specialists are experienced in the mesothelioma diagnostic process. This knowledge gap among medical professionals can delay diagnosis. Patients may need to seek a second opinion.
The Mesothelioma Diagnostic Process in 4 Steps

The Mesothelioma Diagnostic Process in 4 Steps

02. Testing for Mesothelioma

How to Test for Mesothelioma

Doctors order a series of tests and procedures to identify the cause of symptoms. A medical team will use imaging scans to identify any tumors and metastasis (spreading). Blood tests can also identify biomarkers that may suggest the presence of mesothelioma. However, biopsies offer the only definitive diagnostic method.

03. Imaging Scans

Mesothelioma Imaging Scans

During the diagnostic process, imaging tests help identify tumors, tumor location and metastasis of cancer. The most common scans used for diagnosing mesothelioma include X-rays, MRIs, CT scans, PET scans and ultrasounds.

  • X-rays: X-rays identify abnormalities and help rule out other conditions. An X-ray can reveal common mesothelioma symptoms, such as pleural effusions (fluid buildup in the lungs) or peritoneal effusions (fluid buildup in the abdomen).
  • CT scans: CT scans distinguish abnormalities within normal organs and tissues. CT scans are an important tool in the diagnosis of all types of mesothelioma.
  • MRI scans: MRIs offer clarity between normal and cancerous tissues. MRIs can detect the spreading of mesothelioma into surrounding tissues. The scan may be used as part of the mesothelioma staging process.
  • PET scans: PET scans distinguish between normal and cancerous tissue by measuring metabolic activity level. These scans are helpful in showing metastasis.
  • Ultrasounds: Ultrasounds provide live images of the body, showing organs, vessels and tissues. For mesothelioma patients, this type of imaging can identify pleural or peritoneal effusions that may need draining.

Mesothelioma patient and survivor Heather Von St. James recounts her reaction when learning about her mesothelioma diagnosis from her doctor.

04. Biopsies

Mesothelioma Biopsies

Biopsies are the only way to confirm the mesothelioma. Mesothelioma biopsies involve removing a fluid or tissue sample for analysis. Through testing, doctors confirm the diagnosis, stage, cell type and type of mesothelioma. Once the diagnosis is confirmed through biopsy, a medical team can determine treatment options.

Mesothelioma Biopsy

There are four types of biopsies that are commonly used for mesothelioma diagnosis.

  • Fluid Drainage: Fluid drainage is the least invasive biopsy option. This test collects fluid from pleural, peritoneal or pericardial effusions using a needle or catheter. The fluid sample may be drained through thoracentesis, an outpatient procedure. However, in most instances, a fluid sample is not adequate to confirm a mesothelioma diagnosis.
  • Needle biopsies: Doctors use a needle biopsy to extract a tissue sample from an affected area. The tissue samples are often taken from the pleura (lining of the lung) or a lymph node.
  • Surgical camera-assisted biopsies: In a camera-assisted biopsy, a small tube with a camera is inserted into an affected area to locate and retrieve a tissue sample for analysis. Types of camera-assisted biopsies used for mesothelioma include thoracoscopy, laparoscopy and mediastinoscopy.
  • Open surgical biopsies: Surgical biopsies are the most invasive biopsy used for mesothelioma diagnosis. This option is used if tumors are difficult to reach with less invasive procedures. Surgical biopsies used for mesothelioma include thoracotomy and laparotomy.
05. Biomarkers and Blood Tests

Mesothelioma Blood Tests and Biomarkers

Blood tests can be used to look for mesothelioma biomarkers, or substances in the blood that suggest the presence of malignant mesothelioma.

For example, healthy mesothelial cells produce normal levels of mesothelin, but malignant mesothelial cells produce higher levels of the protein. Blood tests can detect increased levels of mesothelin and aid diagnosis.

Effective Mesothelioma Blood Tests and Biomarkers
  • SOMAmer
  • MPF
  • Fibulin-3
  • CA-125
  • N-ERC/Mesothelin Test
  • Osteopontin
  • Il-6

However, there is currently no blood test that can definitively diagnose mesothelioma. Research is ongoing to find new and more effective biomarkers for mesothelioma.

Diagnostic Efficacy of Biomarker Testing
Sensitivity1 Specificity2
SOMAmer 92% 88%
MPF 34% 95%
Fibulin-3 96.7% 95.5%

1: Sensitivity: the test’s ability to correctly identify those with mesothelioma.
2: Specificity: the test’s ability to correctly identify those without mesothelioma.

Mesothelioma Pathology

Mesothelioma pathology is the microscopic study of the disease using a tissue or fluid sample from a biopsy. There are two forms of pathology: histology and cytology.

Histology focuses on the individual cell level, while cytology studies how the cells are forming, spreading and interacting within the body.

A pathologist uses histology and cytology to confirm a mesothelioma diagnosis. The evaluation can also determine the stage of the disease and help prevent misdiagnosis.


Histology analyzes tissue samples, looking at the anatomy of the cells to determine malignancy, mesothelioma cancer type and cell type. Histologic biopsy samples are almost always needed by pathologists to confirm mesothelioma.


Cytology analyzes tissue or fluid samples, looking at the appearance of individual cells and groups of cells to better characterize them and make a diagnosis. Pathologists are typically not able to confirm a diagnosis of mesothelioma using cytology alone.

06. Misdiagnoses

Common Mesothelioma Misdiagnoses

Mesothelioma is a rare cancer often mistaken for more common diseases and conditions. Each step of the diagnostic process, especially a biopsy, is crucial to preventing misdiagnosis.

If mesothelioma is mistaken for another condition, treatment will be delayed, which can worsen a patient’s prognosis. Misdiagnoses vary by type, as listed below.

Pleural Mesothelioma
  • Adenocarcinoma
  • Asthma
  • Bronchial infections
  • Chronic obstructive pulmonary disease (COPD)
  • Emphysema
  • Other lung cancers
  • Pneumonia
Peritoneal Mesothelioma
  • Benign cystic mesothelioma
  • Crohn’s disease
  • Hernia
  • Irritable bowel syndrome (IBS)
  • Other abdominal cancers
  • Ovarian cancer
Pericardial Mesothelioma
  • Coronary artery disease
  • Heart failure
  • Heart-related cancers
  • Synovial sarcoma
  • Tuberculous pericarditis
Testicular Mesothelioma
  • Adenocarcinoma
  • Epididymitis
  • Inguinal hernia
  • Testicular cancers
07. Early Detection

Importance of Early Detection of Mesothelioma

When diagnosed early, mesothelioma treatment is more effective. Early diagnosis and treatment are critical because the cancer is aggressive and spreads quickly. Although there is no cure, mesothelioma treatment may be able to extend life expectancies for patients.

Patients diagnosed with stage 1 mesothelioma or stage 2 mesothelioma are typically able to undergo aggressive surgeries and multimodal treatment. These treatments have shown success in extending survival. Those diagnosed at stage 3 or stage 4 mesothelioma often have limited treatment options and a less favorable prognosis.

Mesothelioma has a long latency period; it can take decades for symptoms to emerge. This delay in symptoms makes early diagnosis difficult. Misdiagnosis is also common due to the rarity and nonspecific symptoms.

However, on average, patient prognosis is becoming more favorable. Improvements in diagnostic tools are increasing the likelihood of early detection. This can lead to a more favorable prognosis.

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