Mesothelioma Pathology

Mesothelioma pathology is the study of the nature of mesothelioma, along with all of its causes and outcomes.

It plays a large role in the diagnosis of asbestos-related illnesses. Studying the way mesothelioma behaves in the body, including how it begins and how it looks, can be an invaluable tool for doctors. It can help to provide a more accurate and complete picture of what the diagnosis and treatment plan will look like for patients.

Cellular Pathology

While just the appearance and visible characteristics of a tumor can often be enough to confidently diagnose a specific type of cancer, other tumors will require a medical professional like a pathologist to study and examine the cells under magnification. With a microscope, a pathologist can generally differentiate between different types of mesothelioma cells and other cancer cells, as well as particular subtypes that may be discernable through either histopathologic features or cytologic features.


Histology revolves around the study of biopsy samples. Histopathology specifically references the study of diseased cells. In the context of mesothelioma, these samples are obtained through a thoracoscopy, which is a type of biopsy that can boast a 98% accuracy rate of a mesothelioma diagnosis. Studying the tumor cells in this manner is the only way to be positive in the diagnosis of which cancer is present in the patient. 

When pathologists use histology to diagnose mesothelioma, they are looking for confirmation of the tumor being one of three types.

The microscopic analysis will determine if the tumor has cells that are either epithelioid, sarcomatoid, or biphasic. Epithelioid cells are cuboid, oval, or polygonal in shape and can sometimes mimic healthy cells. Sarcomatoid cells are shaped like spindles. Biphasic tumors contain a mix of sarcomatoid and epithelioid cells.


Cytology is the study of cells from fluids or scrapings of the surface without invasive tissue sampling.

Pathologists will often gather pleural fluid, called effusion, from a patient with suspected cancer of the pleura or pleural space. This is taken with fine-needle aspiration and is a quicker and cheaper method of getting a sample for biopsy.

Cytology is often able to identify the presence of a particular malignant cancer cell, but it cannot tell the difference between a malignant tumor and an invasive tumor. Histological testing would still be needed to confirm a diagnosis of mesothelioma.

Peritoneal Mesothelioma Pathology

When compared to primary pleural tumors are very similar to peritoneal mesothelioma on a purely histologic basis. It is important to note that the biphasic cell type is the least common and it also has a poor prognosis compared to other types.

The well-differentiated papillary mesothelioma, a benign mesothelioma subtype, is more often seen in the lining of the abdomen, called the peritoneum, than in the pleura. These cells are generally easy to identify, as they have a smooth appearance, are contoured, and lack nucleoli entirely. This cell type has a good prognosis, but relapse is also more likely to become malignant.