Mesothelioma cell types are divided into three primary types of cells – epithelial, sarcomatoid and biphasic. Additional mesothelioma cell types include heterologous cells, benign cells, and other rare cell types.

Properly diagnosing which cell type is responsible for each patient’s disease is essential to ensuring proper treatment and for providing an accurate prognosis.

Epithelial Mesothelioma Cells

Epithelial cells form the epithelium, the most common type of tissue found in the human body. The epithelium is a similar tissue in the body as the mesothelium.

The epithelium is a lining of hollow tube-shaped blood vessels and the mesothelium covers the outer linings of organs such as the lungs, heart, and testes.

Epithelial mesothelioma occurs in the epithelium and is the most common type of mesothelioma, making up 50-70% of all mesothelioma diagnoses.

When cancer infects epithelial cells, they become malignant epithelioid cells. Epithelioid cells do not spread easily throughout the body since the nature of epithelial cells is immobility and close adherence to one another.

These particular types of cells respond better to treatment than all other types of mesothelioma cells and include multiple subtypes.

It is important to understand which type of cells are malignant in order to determine the proper course of treatment and avoid a misdiagnosis.

A histologist is a professional who has the expertise to determine which type of cells have been mutated into malignant cells.

Adenomatoid mesothelioma — also known as glandular or micro glandular mesothelioma, is one of the most common subtypes of epithelial mesothelioma. Adenomatoid mesothelioma cells are flat or cube-shaped and can develop both malignant and benign tumors.

Benign tumors, or lesions, can develop in various places throughout the body including the genital tract, pancreas, bladder, liver and adrenal glands.

These benign tumors are relatively easy to remove during surgery. Malignant mesothelioma tumors, however, develop in the pleural lining of the lungs and are difficult to remove even with surgery, chemotherapy, and radiation.

  • Cystic mesothelioma — a very rare form of mesothelioma that develops most commonly in the lining of the abdominal cavity of reproductive young and middle-aged women. Also known as benign multicystic peritoneal mesothelioma, benign papillary peritoneal cystosis, postoperative peritoneal cysts and multilocular peritoneal inclusion cysts, this form of cancer is localized and does not spread to other parts of the body. Additionally, this type of mesothelioma has no clear link to asbestos. Rather, studies suggest it develops in response to female hormones, prior surgery, endometriosis or foreign fibers.
  • Deciduoid mesothelioma — is very rare, typically found in the abdomens of females and is associated more with hormonal imbalances than asbestos exposure. Deciduoid mesothelioma is composed of large polygonal and oval-shaped cells packed closely together to form a firm, grayish tumors. A cure for these tumors has yet to be discovered, so treatment involves controlling symptoms and prolonging the patient’s life expectancy with combinations of standard cancer therapy like surgery, chemotherapy, and radiation. Unfortunately, this type of cancer is difficult to diagnose, leaving patients with an average life expectancy of five or six months after its discovery.
  • Papillary mesothelioma — is a rare form of epithelial mesothelioma that most commonly develops in the abdominal lining of females and is not necessarily linked to asbestos. Papillary mesothelioma tumors are well-differentiated, or low-grade, which means that the cancer cells multiply slowly and often do not spread into other parts of the body. The tumor’s cells are composed of microscopic, finger-like projections known as papillae, thus providing the name papillary mesothelioma.These cells are often entirely inactive, leading to a much better prognosis and life expectancy than other mesothelioma cancers. Five to ten percent of patients survive five years after being diagnosed, and some diagnosed patients have survived for decades.
  • Small cell mesothelioma — is another rare type of cancer typically considered to be a subtype of epithelial mesothelioma. One study, however, suggested that some of the small cells were biphasic, displaying features of both epithelial and sarcomatoid mesothelioma.

This cancer is so named because the tumors are composed of cancer cells much smaller than other mesothelioma cancer cells. These small cancer cells are round in appearance, each with a single-bland nucleus that makes up the majority of the cell.

This type of cancer is difficult to diagnose because of its apparent similarity to other types of diseases, so doctors must take biopsies and run immunohistochemical tests to make an accurate diagnosis.

Sarcomatoid Mesothelioma Cells

Sarcomatoid mesothelioma cells are the least common of the three main types of mesothelioma cells. These cells make up 10-20 percent of mesothelioma cells found in the lining of the lungs and less than four percent of those found in the lining of the abdomen.

Also known as sarcomatous, diffuse malignant fibrous and spindled mesothelioma due to their shape, these mesothelioma tumors are also the most aggressive and the most difficult to treat.

These cells also mimic other diseases, making them harder to diagnose. After patients are diagnosed, however, their average life expectancy is less than six months.

There are a few subtypes of sarcomatoid mesothelioma cells, all of which are associated with asbestos exposure.

  • Desmoplastic mesothelioma cells — are most commonly classified as a subtype of sarcomatoid mesothelioma cells, but they have occasionally been diagnosed with epithelial and biphasic cells. These bland, patternless cells form a dense, fibrous tissue in the lining of the lungs, and occasionally the lining of the abdomen, with frequent nodules throughout. This is one of the criteria for diagnosing desmoplastic mesothelioma, along with specific sites with cell decay, the spread of the tumor to nearby tissues like lungs, skeletal muscle or fatty tissue, sections with increased cellularity, the presence of the p53 gene protein and neoplastic spindle cells spreading to the chest wall or lungs. Chest pain caused by fluid buildup in the lungs is the most common symptom of this type of cancer.
  • Lymphohistiocytic mesothelioma — is an especially rare subtype of mesothelioma, accounting for less than 1 percent of all asbestos-related cancer diagnoses. This disease is often misdiagnosed as lymphoma due to the presence of inflammatory immune cells such as lymphocytes, plasma cells, and macrophages. These inflammatory cells form dense bundles that form tumors solely in the lining of the lungs, causing symptoms of chest pain, fatigue, and weight loss.Treatments for lymphohistiocytic mesothelioma are standard for other cancers, but this unique type has shown more promising outcomes including cases of spontaneous remission possibly due to the immune cells making up the tumors.

Biphasic Mesothelioma Cells

Biphasic mesothelioma cells are the third main type of mesothelioma cell and contain multiple types of other mesothelioma cell types.

This makes a diagnosis challenging since biopsies will most likely only yield multiple cell types if multiple biopsies of the tumor are taken.

Cancer treatments are most effective when tailored to the particular type of cancerous cell, so misdiagnosing biphasic mesothelioma can lead to insufficient treatment.

Because sarcomatoid mesothelioma cells are so much more aggressive than epithelial mesothelioma cells, the treatment and prognosis of each individual case of biphasic mesothelioma depend on the ratio of these cells within the biphasic cells.

Patients with more epithelial cells generally receive a better prognosis, while patients with more sarcomatoid cells receive a poorer prognosis.

Rare Mesothelioma Cell Types

Mesothelioma as a whole is a rare disease, and sarcomatoid mesothelioma cells are the rarest of the three main types of mesothelioma cells.

There are additional rare types of mesothelioma cells that do not fit into the three main types, though, including heterologous mesothelioma cells and benign mesothelioma cells.

Heterologous Mesothelioma Cells

Heterologous mesothelioma is such a rare form of asbestos-related cancer that researchers have yet to formulate a proper definition of the disease because it is still so little understood.

Heterologous mesothelioma cells are unique because they contain bodily elements different from the tissue type in which the cells formed.

Researchers have discovered bone, cartilage and soft tissue cells in these heterologous mesothelioma cells that form mainly in the lining of the lungs and, to a smaller extent, in the lining of the abdomen.

They suspect that the mesothelioma cells, which are mutations of the mesothelial tissue that lines several thoracic cavities, undergo cellular differentiation.

Cellular differentiation normally occurs while cells are forming and are what causes them to grow into cells specialized for certain tasks.

Because the mesothelioma cells are mutated, however, it is possible that they mutate the process of cellular differentiation, enabling them to perform multiple tasks like forming bone tissue where there was none.

Incoming data and ongoing research are still shaping the treatments and prognoses for heterologous mesothelioma patients.

Benign Mesothelioma

Benign mesothelioma is a rare, noncancerous form of mesothelioma that is not caused by asbestos exposure.

The factor that causes these cells to be benign is the fact that they do not invade nearby cells or travel throughout the body.

Therefore, patients with benign mesothelioma many times have more positive prognoses and successful treatment options.

The cells can, however, cause tumors that continue to grow larger, and they can recur after surgery or other treatments.

Symptoms and diagnostic procedures are similar to those of malignant mesothelioma. Treatments differ in that surgery is normally the only necessary procedure.

Chemotherapy and radiation are unnecessary since the disease is not spreading to other parts of the body.

There are multiple subtypes of benign mesothelioma, including a few that overlap with other mesothelioma types such as well-differentiated papillary mesothelioma and adenomatoid tumors.

Other types include benign multicystic peritoneal mesothelioma and localized fibrous tumor.

Have you or a loved one recently been diagnosed with the aggressive cancer mesothelioma due to asbestos exposure? Contact Mesowatch today for support, a free legal case evaluation and to be connected with a legal team to help you build your case.