Written By: Devin Golden
Mesothelioma pathology is part of the process for a mesothelioma diagnosis. It is the next step following a biopsy and examines tissue or fluid samples.
Medically Reviewed By
Karen Ritter, RN BSN
Registered Nurse
Medically Reviewed By
Karen Ritter, RN BSN
Registered Nurse
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Important Facts About Mesothelioma Pathology
Mesothelioma pathology is the study of tissue or fluid samples to determine if mesothelioma is present, along with specific characteristics of the disease. Pathologists conduct the mesothelioma pathology process.
The mesothelioma diagnostic process begins with imaging tests. Doctors look for abnormalities in scans, which indicate the presence of this cancer. However, the only definitive way to diagnose mesothelioma is through a biopsy.
A mesothelioma biopsy is a medical procedure to extract tissue or fluid from wherever doctors believe the disease exists. Following the biopsy, the surgeon sends the tissue or fluid samples to a pathologist, who examines it. They’ll create a pathology report about the findings.
Part of mesothelioma pathology is immunohistochemical staining, which helps pathologists determine if mesothelioma is present. This scientific practice also reveals which cell types are present in the samples.
Staining reveals antibodies or proteins, also called “immunohistochemical markers.” The immunohistochemical markers for pleural mesothelioma include:
Calretinin
Demonstrated in nearly all epithelioid mesothelioma cases
Cytokeratin 5 or 5/6
Expressed in between 75% and 100% of cases
Wilms’ tumor-I antigen (WT1)
Shown in between 70% and 95% of diagnoses
Podoplanin (D2-40)
Demonstrated in between 90% and 100% of cases
There are multiple sections to a mesothelioma pathology report, which can be long and complex. The most essential parts are the descriptions of the tissue or fluid samples and the diagnosis section.
The sections of a mesothelioma pathology report include:
This report is based on data compiled from either a histology test or a cytology test (or both). Histology and cytology are separate medical terms within pathology testing and reports. Which one your pathologist performs depends on whether you undergo a tissue biopsy or have fluid removed.
Cytology is the study of cell structure and cells’ functions. This term can be interchangeable with cytopathology, which is the examination of diseases at the cellular level.
In the case of studying mesothelioma, pathologists analyze fluid samples to learn more about the potential presence of malignant cells. Doctors use a needle to extract fluid buildup in either the pleura or the peritoneum. Pathologists then stain the fluid to see if malignant cells react to the stain.
Mesothelioma cytology involves a less-invasive diagnostic procedure than a tissue biopsy. Doctors won’t make a large incision or use a thick needle to remove fluid.
However, a definitive diagnosis using fluid samples is challenging. There are often not enough malignant cells in the sample to determine if a patient has mesothelioma. Pathologists also have difficulty analyzing the cells in the sample.
“It’s harder to examine the architecture of the individual cells suspended in the fluid,” said Dr. Elliot Wakeam, a thoracic oncologist at Michigan Medicine.
For these reasons, many mesothelioma doctors and pathologists prefer tissue samples and histology for mesothelioma pathology.
Histology is the study of tissue under a microscope. The term is interchangeable with histopathology, which is the study of diseases in tissue.
For mesothelioma, pathologists conduct histology testing by examining extracted tissue for malignancies. Doctors retrieve this tissue one of two ways: from a surgical biopsy, which involves a large incision; or from a needle biopsy, which requires a small incision.
Histology can be in unison with cytology testing to study both tissue and fluid samples. However, tissue samples provide more conclusive evidence of whether or not mesothelioma is present. The tissue usually provides more cells to study, and the cells are easier to examine without fluid present.
Pathologists stain these cells to uncover the presence of cancer. This staining also allows doctors to determine the mesothelioma cell type. This can affect the patient’s treatment options and mesothelioma prognosis.
One of the main reasons for a mesothelioma pathology report is to determine the cell type. Mesothelioma tumors can be made up of three cell variations, each with their own unique qualities and effects on prognosis.
Epithelioid mesothelioma is the most common cell type of this cancer. The characteristics include a clearly defined egg shape with a visible nucleus and pink cytoplasm. Epithelioid mesothelioma is the most treatable cell type because they tend to stick together and are easier to remove surgically.
Sarcomatoid mesothelioma is the least common cell type. Sarcomatoid mesothelioma cells are spindle-shaped, often overlap one another and show multiple elongated nuclei. Sarcomatoid cells spread quickly throughout the body since they don’t stay clumped together.
Biphasic mesothelioma is a combination of epithelioid cells and sarcomatoid cells. It is the second most common mesothelioma cell type. The cancer must have at least 10% of each cell to be biphasic mesothelioma. Treatment and prognosis depends on which cell type is more prevalent. Patients with more epithelioid cells than sarcomatoid cells have longer life expectancy.
Pathologists analyze tissue and fluid samples extracted from biopsies. Mesothelioma pathology explicitly tests these samples for diseased mesothelial cells, which can form clumps called tumors. Pathologists examine cells under a microscope and use a staining process to detect cancerous proteins specific to mesothelioma.
The pathology report includes the patient’s name and other identifiable information, medical history, the pathologist’s description of the biopsy sample without using a microscope, the microscopic characteristics and the diagnosis.
Pathology is the scientific process to determine if the sample removed from a biopsy includes mesothelioma. Pathologists are integral to properly diagnosing this disease. Pathology also can determine the cell type and stage of the cancer.
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