After analyzing patient symptoms and medical history, doctors will use imaging scans, blood tests, biomarkers and biopsies to diagnose mesothelioma. Due to the typical aggressive nature of mesothelioma, early detection and avoiding misdiagnosis are key to ensuring the best prognosis for the patient.
Imaging scans are used to identify tumors and potential metastasis, while blood tests look for biomarkers that could suggest the presence of mesothelioma. However, biopsies are the only definitive method to diagnose mesothelioma.
How Is Mesothelioma Diagnosed?
When a patient presents symptoms of mesothelioma, doctors will conduct a physical exam, look at the patient’s medical history and begin to rule out more common diseases and conditions. Physicians will then order a series of tests and procedures to identify the cause of symptoms.
Imaging tests help identify tumors, tumor location and metastasis of cancer during the diagnostic process. The most common scans used for diagnosing mesothelioma include X-rays, MRI scans, CT scans, PET scans and ultrasounds.
- X-rays: X-rays provide 2D images of bones and soft tissues to identify abnormalities and help rule out other conditions. Chest X-rays or abdominal X-rays are the most common for mesothelioma, and can reveal common presenting mesothelioma findings like pleural effusions or abdominal ascites (fluid buildup around the lungs or in the abdomen).
- CT scans: CT (computed tomography) scans provide 3D visuals of the body, distinguishing abnormalities within normal organs and tissues. These are used as an important tool in the diagnosis of all types of mesothelioma and to follow up after treatment.
- MRI scans: MRI (magnetic resonance imaging) scans provide 3D, detailed images of bones and soft tissues, offering clarity between normal and potentially cancerous tissues. MRI imaging can be useful in detecting invasion of mesothelioma into surrounding tissues, as part of staging and pre-surgical workup.
- PET scans: PET (positron emission tomography) scans use nuclear imaging technology to identify high metabolic activity of cancer cells and distinguish between normal and cancerous tissues. These scans are helpful in showing metastasis to nearby lymph noeds or distant areas of the body.
- Ultrasounds: Ultrasounds provide live images of the body, showing organs, vessels and tissues, and help to identify tumors after symptoms emerge. In mesothelioma, this type of imaging can be used to identify pockets of pleural effusions/ascites that may need to be drained.
Blood tests can be used to look for mesothelioma biomarkers, or substances in the blood that can 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, which may be detected during blood tests, aiding diagnosis.
There are a variety of blood tests that can be used to identify particular byproducts common for mesothelioma patients, as well as many biomarkers that continue to emerge. Biomarkers may suggest the presence of mesothelioma that may then lead to further evaluation and earlier diagnosis. Biomarkers can also be used to track how well treatments have worked. Currently, there is no blood test that can definitively diagnose mesothelioma.
Mesothelioma blood tests and biomarkers that have shown utility include:
- N-ERC/Mesothelin Test
Biopsies are the most important step in a mesothelioma diagnosis and the only way to confirm the cancer. Mesothelioma biopsies remove cancerous fluid or tissue for analysis that will then be used to confirm the diagnosis and histologic type of mesothelioma, as well as determine treatment options. There are four types of biopsies that are common for mesothelioma, including needle biopsies, camera-assisted biopsies and surgical biopsies.
- Fluid drainage: Drainage of pleural/pericardial effusions or abdominal ascites fluid using a needle or catheter is the least invasive, using a needle or catheter to extract a fluid sample from the affected area. Types of fluid drainage procedures include thoracentesis, paracentesis and pericardiocentesis. However, while results may be suggestive, in most instances a fluid sample is not adequate to confirm a mesothelioma diagnosis.
- Needle biopsies: Also one of the least invasive biopsies, this involves the use of a needle to extract a tissue sample from an affected area such as the pleura or an involved lymph node.
- Surgical camera-assisted biopsies: Camera-assisted biopsies are minimally invasive, using a small tube with a camera to visually 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, often used if tumors are difficult to reach with needle or camera-assisted biopsies. Types of surgical biopsies used for mesothelioma include thoracotomy and laparotomy.
Mesothelioma pathology describes the microscopic appearance of mesothelioma within a tissue sample or fluid. Histology and cytology are two types of pathology specimens created from a biopsy procedure which are then microscopically evaluated by a pathologist to confirm a mesothelioma diagnosis, providing information that will guide staging and diagnosis, while helping prevent misdiagnosis.
- Histology: Histology focuses on tissue samples, looking at the anatomy of the cells and surrounding findings to determine malignancy, mesothelioma cancer type and if the cell type is epithelial, sarcomatoid or biphasic. Histologic biopsy samples are almost always needed by pathologists to confirm a diagnosis of mesothelioma.
- Cytology: Cytology focuses on tissue or fluid samples to look 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 from a cytology sample alone.
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: Pneumonia, emphysema, asthma, bronchial infections, Chronic Obstructive Pulmonary Disease (COPD), adenocarcinoma and other lung cancers
- Peritoneal mesothelioma: Benign cystic mesothelioma, Irritable Bowel Syndrome (IBS), Crohn’s Disease, hernia, ovarian cancer and other abdominal cancers
- Pericardial mesothelioma: Coronary artery disease, heart failure, tuberculous pericarditis, synovial sarcoma and other heart-related cancers
- Testicular mesothelioma: Epididymitis, testicular cancer, inguinal hernia, adenocarcinoma and other testicular cancers
Importance of Early Detection of Mesothelioma
Malignant mesothelioma is an aggressive cancer that spreads quickly. While there is no cure for this cancer, mesothelioma treatment may be able to extend life expectancies for patients, especially if the disease is caught early.
Patients diagnosed at stage 1 or stage 2 are typically able to undergo aggressive surgeries and multimodal treatment, which have shown success in extending survival. Those diagnosed at stage 3 or stage 4 have more limited treatment options and a worse prognosis.
Resources Available for Mesothelioma Patients and Their Families
- More on Mesothelioma Biopsies in our Free Mesothelioma Guide
- Connect with Top Mesothelioma Doctors
- Locate the Nearest Comprehensive Cancer Center
Mesothelioma has a long latency period, and it can take decades for symptoms to emerge, making an early diagnosis difficult. Misdiagnosis is also common due to the rarity and nonspecific symptoms. However, awareness of a prior history of asbestos exposure coupled with improvements in diagnostic tools offer hope that the cancer can be caught early, presenting patients with the best prognosis possible.
Author: Linda Molinari
Editor in Chief, Mesothelioma Cancer AllianceRead about Linda
Reviewer: Dr. James Stevenson
Medical Reviewer and Thoracic Medical OncologistRead about Dr. Stevenson
American Cancer Society. Early Detection, Diagnosis, and Staging.
American Cancer Society. How Is Malignant Mesothelioma Diagnosed? Updated February 2016.
American Cancer Society. Types of biopsies used to look for cancer. Updated July 2015.
American Lung Association. Diagnosing and Treating Mesothelioma. Updated April 2018.