Mesothelioma cytology is sometimes part of diagnosing this rare and aggressive cancer. Doctors can look at fluid samples under a microscope to examine cells for evidence of mutation.
Written by Jenna Campagna, RN
What Is Mesothelioma Cytology?
Mesothelioma cytology, or mesothelioma cytopathology, is the study of cells for the presence of mesothelioma. It is a part of mesothelioma pathology, which is the study of tissue or fluid.
The broad term “cytology” refers to the study of cell structure and how cells function. Cytopathology is the inspection of cells for diseases. Cytopathology and cytology are used interchangeably.
The most notable characteristics of mesothelioma cytology are:
- Less invasive process than tissue biopsy (mesothelioma histology)
- Often requires a small needle incision to perform
- No scar for the patient at the incision area
- Usually doesn’t require anesthesia for the patient
- Easier to acquire samples
- Less expensive than a tissue biopsy
- Not as reliable compared to examining tissue samples
- Fewer cells to analyze in fluid samples compared to tissue
How Is Mesothelioma Cytology Performed?
Mesothelioma cytology starts with a procedure to remove fluid from the patient’s body. Doctors take fluid samples from patients with mesothelioma symptoms.
If doctors see signs of this cancer on imaging tests, they may request a mesothelioma biopsy. Some biopsies involve tissue extraction, and others remove fluid samples.
How Are Fluid Samples Collected?
Fluid samples are collected through non-surgical needle biopsies, often with fine-needle aspirations. Doctors use a syringe with a thin needle to remove fluid from a suspected tumor area.
There are multiple procedures to remove fluid for mesothelioma cytology. They differ based on where your cancer originates.
The non-surgical biopsies used to collect fluid samples are:
- Thoracentesis — Removes fluid from the pleura or lung cavity to diagnose pleural mesothelioma
- Paracentesis — Removes fluid from the peritoneum or abdominal cavity to diagnose peritoneal mesothelioma
- Pericardiocentesis — Removes fluid from the pericardium (surrounds your heart) to diagnose pericardial mesothelioma
Patients often experience fluid buildup in the space where this cancer forms. This is from one of three symptoms:
These symptoms are:
- Pleural effusions — fluid in the pleura, which is between your lung cavity and chest wall
- Ascites — fluid in the peritoneum, which surrounds your abdomen
- Pericardial effusions — fluid in the pericardium
Once the fluid is retrieved, doctors send it to a pathologist for mesothelioma cytology. The result is a cytology report, also called a pathology report, which details the findings and may provide a mesothelioma diagnosis.
How Do Doctors Test Fluid Samples?
The process for testing fluid samples can vary depending on the number of cells and amount of blood collected. Samples with a lower cell count will require a doctor to use a high-powered microscope. Blood-stained samples may require solutions (such as saline, which is a combination of sodium chloride and water) to dilute the blood.
Fluid samples are put on slides and dipped into a collection of stains, or chemical dyes. These stains show evidence of cancer.
Each stain is attracted to certain antibodies or other proteins in the cancer cell and causes a reaction that changes the cell’s color. Pathologists observe this under the microscope and can assess whether the fluid sample contains malignant mesothelioma cells or not.
Microscopic Fluid Sample
The three most common stains for mesothelioma cytology are:
Each stain is attracted to certain antibodies in the cancer cell and causes a reaction that changes the cell’s color. Pathologists observe this under the microscope and can assess whether the fluid sample contains malignant mesothelioma cells.
By looking at the size and shape of cells, pathologists identify the mesothelioma cell types. This is how pathologists determine if a mesothelioma is composed primarily of epithelioid cells or sarcomatoid cells. Each cell type is associated with specific antibodies that show up in staining.
Research suggests that cytology is most useful in diagnosing epithelioid mesothelioma. This cell type makes up between 50% and 70% of all mesothelioma cases. Epithelioid is known for being easy to distinguish.
Limitations of Mesothelioma Cytology
Mesothelioma cytology reports are not always reliable for diagnosing mesothelioma. There are three predominant reasons the process limitations:
- Too few cells in a sample — Not all fluid samples have an adequate amount of cells to examine. This makes it difficult to determine if the disease is mesothelioma or one with similar traits.
- Difficult to examine cells in fluid — Dr. Elliot Wakeam, a thoracic oncologist at Michigan Medicine, is experienced in diagnosing mesothelioma. He said cytologists often have difficulty analyzing “the architecture of individual cells suspended in fluid.”
- Not reliable for determining all cell types — While mesothelioma cytology can identify epithelioid mesothelioma cells, it is not reliable for diagnosing sarcomatoid mesothelioma. A report in the British Journal of Cancer also reported that fluid samples aren’t reliable for diagnosing biphasic mesothelioma.
How to Get an Accurate Mesothelioma Diagnosis
If your cytology report provides inconclusive results, the doctor will likely order a mesothelioma pathology report by way of a tissue biopsy. This is called a mesothelioma histology report.
Camera-assisted tissue biopsies, according to one study published on UpToDate, had 98% accuracy in diagnosing mesothelioma. Fluid biopsies were only accurate in 26% of cases where this method was used.
Mesothelioma pathologists almost always request a tissue biopsy following a mesothelioma cytology report. Most pathologists are reluctant to make a definitive diagnosis solely on fluid samples. Furthermore, you may get more reliable information about the cell type from a histology report rather than just a cytology report.
Last Edited: March 19, 2021.