Histology, or examining a tissue biopsy, is the only current conclusive way to diagnose pleural mesothelioma. It’s considered a much more reliable method than mesothelioma cytology—withdrawing fluid from pleural effusions.

However, mesothelioma cells often appear in the liquid first, so researchers are trying to improve cytology methods to ensure the disease gets diagnosed before treatments become ineffective.

A Brief Look at Histology

Histology, which studies microscopic disease cells, is a subspecialty of pathology. To perform a histological test, doctors conduct a tissue biopsy.

Doctors cut part of the tumor off, collect the samples to send to a pathologist who performs the following tests:

  1. A gross examination, the pathologist studies the sample with their eyes alone to determine which parts of it need to be examined further.
  2. The pathologist will process the sample for a few hours in a small container before placing it in a wax mold. When the wax solidifies, the sample is sliced into thin pieces, put on a glass slide and dyed to emphasize differences between the cells. Using an electron microscope, the pathologist examines the tissue sample for cell shape, size, composition and general behavior to determine if there are any epithelioid, sarcomatoid or biphasic mesothelioma cells in the sample.

Because tissue biopsies require a tissue sample of the tumor, histological examinations happen after the presence of a growth and the doctors are confident they know where the tumor is.

A Brief Look at Cytology

Cytology is another subspecialty of pathology. This branch studies the cells within the body’s fluids. Gathering a sample for cytology is much less invasive because a needle can extract the fluid out of the lining of the lung or heart, instead of a surgical procedure.

One of the reasons it’s difficult to get an accurate mesothelioma cytology diagnosis is the doctor needs to collect a minimum sample of 20 mL, about 4 teaspoons. Having more fluid than 20 mL means the cytologist has a greater ability to get an accurate diagnosis.

Once the fluid is collected and sent to the lab, the cytologist will smear it onto several slides and dye them. This causes the cells to become more visible under a microscope. The cytologist studies how the cells react to the dyes and whether the cells match the images of existing reference slides and databases for mesothelioma.

Doctors prefer to use mesothelioma cytology to diagnose before turning to histology because it is less invasive. But, if the cytologist suspects the patient has mesothelioma, then the patient will need a tissue biopsy to confirm the diagnosis.

Reliability of Cytology vs. Histology

Unlike histology, which can determine if a patient has mesothelioma, cytology has an accuracy rating between 32% and 93%. As cytologists become more familiar with mesothelioma cells and the different ways they present themselves within the fluid, the diagnostic method will continue to improve.

If the researchers can examine more than one sample from a patient, and the sample is correctly prepared, the accuracy of diagnosis is 85%. Until it is as accurate as histology, it is crucial for patients to continue to follow-up with a biopsy if mesothelioma is suspected.

Why Mesothelioma Cytology Is Important

Because mesothelioma cytology is not used as a sole diagnostic method, it can seem strange to do it at all. But there are several reasons why cytology is so essential.

First of all, it’s less invasive than histology. A patient will recover faster, and patients who aren’t well enough to undergo surgery can still get tested.

More importantly, the earliest indications of mesothelioma are often extra fluid building up in the linings. If pathologists can determine whether or not a patient has mesothelioma from the excess fluid alone, then the patient will be able to begin treatment earlier.

The earlier a patient can start cancer treatment the more effective it can be. So, while mesothelioma cytology still has a way to go to be as accurate as histology, it’s important that researchers continue to use it to try and diagnose mesothelioma earlier.

For more information about pleural mesothelioma diagnosis, contact a Patient Advocate today. Call us at (800) 584-4151 or receive a FREE Mesothelioma Help Guide for more information on working with a top specialist.

View Author and Sources

  1. Anders Hjerpe, Sulaf Abd-Own, and Katalin Dobra (2018) Cytopathologic Diagnosis of Epithelioid and Mixed-Type Malignant Mesothelioma: Ten Years of Clinical Experience in Relation to International Guidelines. Archives of Pathology & Laboratory Medicine: August 2018, Vol. 142, No. 8, pp. 893-901. Retrieved from: https://doi.org/10.5858/arpa.2018-0020-RA. Accessed August 17, 2018.
  2. Nguyen, G. "Essentials of Fluid Cytology." Retrieved from: https://pathology.ubc.ca/files/2012/06/FLUIDCYTOLOGYBook09R1.pdf. Accessed August 17, 2018.

Last modified: September 1, 2018