Types of Mesothelioma Guide

There are several different types of mesothelioma based on tumor location and cell type. The most common types are pleural and peritoneal mesothelioma. Epithelioid is the most common cell type.

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Mesothelioma Types

On average, around 3,000 new mesothelioma cases are diagnosed annually in the United States. The majority of malignant mesothelioma patients tend to be Caucasian males in their late 50s, 60s, and 70s exposed to asbestos decades earlier.

Most of these victims were exposed while working, typically at plants, steel mills, factories, or on military bases. A smaller subgroup of mesothelioma patients includes non-white males, younger white males, and women.

Women were exposed while working as military nurses, as teachers, or through second-hand asbestos contact through their family members.

There are several types of mesothelioma categorized by the location of the primary tumor:

• Pleural Mesothelioma: Pleural mesothelioma attacks the protective lining of the victim’s chest and lungs, specifically the thin membrane of cells lining the lungs. Often, pleural plaques will develop around the lungs and chest. This is a good indication that the victim may have pleural mesothelioma.
• Peritoneal Mesothelioma: This form of mesothelioma is found in the abdominal area and associated organs. Cancer specifically attacks the peritoneum. This is one of the rarest forms of mesothelioma, with only around 500 diagnosed cases in the United States each year.
• Pericardial Mesothelioma: Pericardial mesothelioma affects the area around the heart, specifically the pericardium (the sac that surrounds the heart). Physicians deduct that asbestos reaches the lining of heart when someone inhales or ingests the fibers and they make their way down the bloodstream and into the pericardium.
• Testicular Mesothelioma: Very rare is mesothelioma that grows in the lining around the testes. Although rare, this type of mesothelioma can be removed surgically and cured in the early stages.

Mesothelioma Histology

One of the reasons why mesothelioma is so difficult to diagnose and treat effectively is that its histology (the microscopic characteristics of cells and tissue) divides asbestos cancer cell types into three distinct groups.

Epithelioid, sarcomatoid, and biphasic are recognized as the three groups; the latter is categorized as a mixed type because it combines genetic traits of both epithelioid and sarcomatoid mesothelioma.

• Epithelial mesothelioma: Epithelioid mesothelioma, or epithelial mesothelioma, accounts for 60-70% of all diagnosed cases. Patients who are treated for epithelioid mesothelioma usually have the best outcomes during treatment. Epithelioid cells have prominent papillo-tubular structures.
• Sarcomatoid mesothelioma: This form of mesothelioma accounts for 10-15% of cases and is more aggressive. Sarcomatoid cells are spindle-shaped and closely resemble true sarcomas, yet these cells differ from epithelioid cells as they have no nucleus. Diagnosis for sarcomatoid mesothelioma is especially challenging as the healthy cells are extremely difficult to differentiate from the cancerous cells.

• Biphasic mesothelioma accounts for 10-15% of cases and is the most aggressive, possibly because it combines genetic elements of both epithelioid and sarcomatoid strains of the tumor. Biphasic cells blend the structural forms of the other two strains of mesothelioma
• Papillary Mesothelioma: This form of mesothelioma is most often diagnosed in female victims. It is a rare type of epithelioid mesothelioma that develops in the lining of the abdomen. Most cases of papillary mesothelioma are benign and the tumors are painless. Since this type of mesothelioma is so rare, there is currently no standard medical treatment.
• Cystic Mesothelioma: This type of mesothelioma is considered rare and benign, and occurs mostly in females. Unlike other forms of the disease, cystic mesothelioma is generally not caused by asbestos exposure.
• Small Cell Mesothelioma: Small cell form of mesothelioma is a rare cell subtype, but it also comes with a grim prognosis. More studies are needed to understand the best course of treatment.
• Heterologous Mesothelioma: This form of mesothelioma is so rare that treatment options at this point are difficult. Scientists and physicians continue to research in order to get more information on the causes and formation of heterologous mesothelioma.
• Deciduoid Mesothelioma: This is an extremely rare subtype with distinct yet extremely different characteristics of the other subtypes. The prognosis for deciduoid mesothelioma is grim, with an average survival rate of around 6 months.
• Lymphohistiocytoid Mesothelioma: This is another rare subtype of mesothelioma, accounting for less than 1% of all diagnosed cases. Studies indicate that prognosis varies according to treatment and each patient’s individual medical history.
• Desmoplastic Mesothelioma: Desmoplastic mesothelioma is another subtype of mesothelioma that’s generally of the sarcomatoid variety. Like many other subtypes, the prognosis is typically poor.

This division of histological factors requires pathologists to perform many tests, including immunohistochemical tests.

However, there is no single test that are 100% accurate or can tell the difference between mesothelioma and carcinoma. Immunohistochemical tests also can’t easily determine whether a tumor is benign or malignant.

Further, the Food and Drug Administration (FDA) has not approved a specific immunohistochemical test, so individual cancer centers use different panels.

Staging of Mesothelioma

Although there are different types of mesothelioma, all forms of the cancer are classified in stages, ranging from stage one through four.

Staging categorizes cancer based on how much of the disease is present in the body. It also measures the spread of cancer from its point of origin to other tissues or organs.

Malignant mesothelioma staging is useful to doctors because it allows them to choose the right treatment options, such as palliative or curative.

Malignant mesothelioma is classified as a Stage Ia-IV cancer, regardless of subtype:

• Stage Ia: Tumor is in the outer layer of the pleura (parietal pleura). It is not in the pleura covering the lung (visceral pleura)
• Stage Ib: Tumor is in both the parietal and visceral pleura
• Stage II: Tumor has spread into the lung or diaphragm.
• Stage III: Tumor has spread to one or more of these organs or areas: the pericardium, part of the chest wall, or lymph glands inside the chest
• Stage IV: Tumor has spread to one or more of the following: across the chest wall or pericardium, various areas of the chest wall, the heart, liver, windpipe or esophagus, or the opposite lung

Since the symptoms of mesothelioma develop slowly and mimic other respiratory or abdominal diseases, it is difficult to detect and diagnose. In many cases, the tumors are not detected until they have reached Stages Ia or II. This makes effective treatment of mesothelioma difficult and reduces the patients’ post-diagnosis survival time significantly.

Your medical team will give you a detailed description of the type of mesothelioma you have when you receive a diagnosis. The type helps inform treatment and prognosis.

Getting Help

If you’ve been injured by asbestos, keep in mind that there is a good chance that you’ll qualify for considerable compensation. Remember to fill out our form to get your free Financial Compensation Packet, with information on experienced asbestos and mesothelioma lawyers in your area. If you have questions or need additional assistance, contact us at 800-793-4540.