What Is Mesothelioma Pathology?

Mesothelioma pathology refers to the study of malignant mesothelioma, a cancer of organ tissue linings. Pathology is the study of disease. The term also refers to the branch of medicine in which doctors called pathologists examine body tissue to diagnose and understand disease.

Did You Know?
Without pathology, doctors would not be able to accurately diagnose mesothelioma.

Doctors use mesothelioma pathology results to accurately diagnose the condition. Treatment depends on this process. Additionally, pathology allows scientists and doctors to better understand how mesothelioma develops and spreads, which can lead to treatment improvements.

Mesothelioma Diagnostic Process

Diagnosing mesothelioma requires doctors to take specific steps, using imaging, tests and biopsy examinations to identify the disease.

How Doctors Diagnose Mesothelioma
  1. A health care professional obtains a medical history and completes a physical exam to identify signs and symptoms of mesothelioma.
  2. Your provider may order imaging tests, such as a chest X-ray and computerized tomography scan of the chest and abdomen, or certain blood tests to look for changes caused by mesothelioma.
  3. When tests suggest mesothelioma, doctors order a biopsy to collect cells and/or pieces of tumor for a pathology examination.
  4. Pathologists examine the sample under a microscope and perform special tests for mesothelioma diagnosis.

After diagnosing mesothelioma, your providers will use your test results to determine its stage. The stage of mesothelioma affects treatment and prognosis. 

Understanding Your Mesothelioma Pathology Report

Pathology reports are descriptions of the tissue, cell, blood sample or part of an organ that was removed during a biopsy. The pathologist who examines the sample completes these reports.

Most people with mesothelioma will receive a pathology report from their doctor at one point or another. Each report contains certain components. Patient Advocate Danielle DiPietro notes, “When speaking with people about their mesothelioma diagnosis and they don’t know their cell type, for example, I explain that it can be found on their pathology report.”

Elements of the Pathology Report
  • Patient Information: Your name, date of birth, patient ID number and/or Social Security number
  • Case Number: The case number identifying the specimen
  • Date and Procedure Type: The date of the procedure used to obtain the sample and its type (blood sample, surgery or biopsy)
  • Medical History: A brief description of your medical history and current clinical diagnosis
  • Specimen Description: A gross description (how it looks to the naked eye) and a microscopic description of the specimen
  • Final Diagnosis: The pathologic diagnosis based on the pathologist’s examination of the sample
  • Pathology Information: The name and signature of the pathologist, along with the name and address of the pathology lab

For people with mesothelioma, the specimen description section of the pathology report will include details about cell type and the markers identified with special staining. Markers of mesothelioma are antigens, which are proteins made by immune cells in response to foreign substances. These antigens appear in mesothelioma cancer cells and help pathologists accurately diagnose the condition. 

Types of Mesothelioma Pathology

The two types of pathology involved in a mesothelioma diagnosis are histopathology and cytopathology. The different categories of pathology are based on the part of the body being studied.

Mesothelioma Pathology Types
  • Cytopathology: Studies cells obtained from body secretions and fluids
  • Histopathology: Involves examination of body tissues, collections of cells with similar behavior that work as a unit

Both types of pathology rely on the microscope for examination. 


Histologic evaluation of a tissue sample is usually required to diagnose mesothelioma. The three cell types of mesothelioma — epithelioid, sarcomatoid and biphasic — are classified based on how a tissue sample looks under the microscope. Each cell type of mesothelioma responds to treatment differently. 

Epithelioid mesothelioma is the most common type and accounts for between 50% and 70% of all mesothelioma cases. Sarcomatoid and biphasic types each represent about 10%-15% and 20%-30% of cases, respectively.

Epithelioid is the most common type of mesothelioma

Immunohistochemical stains use antibodies to detect certain substances in a tissue sample that can help tell mesothelioma apart from similar-looking cancers, such as types of lung cancer. These stains change the color of the sample based on which antigens are present.


Mesothelioma cytology involves examining the fluid in the pleural cavity. The pleural cavity is the space between the pleura, the two tissue layers that cover the lungs and chest wall. In a person with mesothelioma, this fluid can contain cancer cells and/or other substances that suggest the presence of cancer. Pathologists can use this information to help with a mesothelioma diagnosis.

fact on cytology in diagnosing mesothelioma

Cytology on its own isn’t enough to diagnose mesothelioma. However, when performed by an experienced pathologist, cytologic evaluation combined with imaging and/or blood testing can help to diagnose mesothelioma. A tissue biopsy with histology testing remains the best way to get an accurate cell-type diagnosis.

What Happens After You Receive Your Pathology Report

Pathology reports guide mesothelioma treatment, so receiving your report will generally lead to a discussion about your potential treatment options. If you receive the report before discussing it with your doctor, it’s important to go over it and identify any questions you have. This initial review allows you to go into your doctor’s visit prepared to discuss your results. 

If you become overwhelmed by the conversation about your diagnosis, know that you’re not alone. Your doctor is there to answer questions and support you. Additionally, if you’re interested in getting a second opinion on your diagnosis and treatment, patient advocates can help connect you with specialists and cancer centers near you.

Along with helping you find doctors, the Patient Advocates at The Mesothelioma Center are available for additional support. Advocates often provide medical resources, help with navigating the health care system and assistance in applying for insurance, among other benefits.