Mesothelioma Cytology

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 and disease.

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Written by Jenna Campagna, RN

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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 to determine if this cancer exists.

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 often 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 who have shown 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 by using fine-needle aspirations. Doctors use a syringe with a thin needle to remove fluid from a suspected tumor area.

There are multiple types of procedures to remove fluid for mesothelioma cytology. The one you undergo depends on where doctors believe your cancer originated.

The non-surgical biopsies used to collect fluid samples are:

  • Thoracentesis — Involves removing fluid from the pleura or lung cavity to diagnose pleural mesothelioma
  • Paracentesis — Involves removing fluid from the peritoneum or abdominal cavity to diagnose peritoneal mesothelioma
  • Pericardiocentesis — Involves removing fluid from the pericardium (surrounds your heart) to diagnose pericardial mesothelioma

Most times, this fluid comes from a symptom related to each type of mesothelioma. Patients often experience fluid buildup in the space where this cancer forms.

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 to conduct 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 to examine them. 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 work quickly to 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.

microfluid sample

Microscopic Fluid Sample

The three most commonly used stains for mesothelioma cytology are:

  • Diff-Quik
  • Papanicolaou
  • May-Grünwald-Giemsa

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.

By looking at the size and shape of cells, pathologists are able to identify mesothelioma cell types. This process 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 due to its elongated, defined egg shape, pink cytoplasm and single nucleus.

Limitations of Mesothelioma Cytology

Mesothelioma cytology reports are not always reliable for diagnosing mesothelioma. There are three predominant reasons mesothelioma cytology has 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, such as adenocarcinoma.
  • Difficult to examine cells in fluid — Dr. Elliot Wakeam, a thoracic oncologist at Michigan Medicine, is experienced in diagnosing mesothelioma. He said that cytologists often have difficulty analyzing “the architecture of individual cells suspended in fluid.”
  • Not reliable for determining all cell types — While mesothelioma cytology is used for identifying epithelioid mesothelioma cells, it is not reliable for diagnosing sarcomatoid mesothelioma. This is according to a report in the British Journal of Cancer, which also said 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: August 3, 2020.

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