MALIGNANT EPITHELIOID MESOTHELIOMA

Introduction to Malignant epithelioid mesothelioma

Malignant epithelioid mesothelioma, also known as malignant mesothelioma is a rare disease characterized by malignancy of the mesothelial cells of the lung and/or pleural space. The condition is usually diagnosed in people older than 35 years.

For many years, Malignant epithelioid mesothelioma was considered rare cancer with relatively high mortality. However, recently a series of case reports have been published that describe cases of MALIGNANT EPITHELIOID MESOTHELIOMA with early-stage (stage I) or stage IIa tumors. As most forms of malignant mesothelioma are inherited, it is strongly suggested that this condition may be more common than previously thought.

What is an Epithelioid Mesothelioma

Epithelioid mesothelioma is a rare type of lung cancer that mostly affects those in their 50s, 60s, and 70s. It is caused by the presence of epithelial-mesenchymal cells (EMC) in the pleural cavity. The two main types are:

  • 1) Follicular Epithelioid Mesothelioma
  • 2) Malignant Epithelioid Mesothelioma

The main features of each type are as follows:

Follicular Epithelial Mesothelioma:

These tumors usually occur in the right pleural space and are usually grayish or brownish in color. They can be detected clinically by the presence of adherent EMC, while they are more easily observed during radiographic examinations. Follicular Epithelial Mesotheliomas can also be seen on transillumination CT scans, but they are not commonly found on this scan.

Malignant Epithelial Mesotheliomas:

These tumors usually occur in the left pleural space, and as a result, are often located in areas where there is a large amount of connective tissue or other tissue such as pleura or lung parenchyma that makes it hard for an EMC to grow and attach to it. They can be detected clinically by the presence of EMC adhering to surrounding tissues with little or no signs of inflammation, while they are more easily observed during radiographic examinations. Malignant epithelial mesotheliomas can also be seen on transillumination CT scans, but they are not commonly found on this scan.

Malignant epithelial mesothelioma may spontaneously regress following surgical removal of all tumor mass, but patients often experience recurring adenopathy within 5-10 years after surgery – sometimes lasting for life if left untreated. When epithelial mesothelioma has spread to lymph nodes and throughout the chest wall as well, it is called Hodgkin’s Lymphoma. This should always be confirmed by blood testing since Hodgkin’s lymphoma is often associated with other blood disorders like hemochromatosis.

What is a Malignant Mesothelioma?

Mesothelioma is a rare cancer of the lung.

Mesotheliomas are composed of epithelioid (or solitary) cells and mesothelial tissue. In a mesothelial tumor, the epithelioid cells are usually larger than the surrounding mesenchymal cells, which are usually smaller, making it fairly easy to spot a malignant tumor. Mesothelioma is extremely rare, with less than 3% of all lung tumors being malignant mesotheliomas.

The most common site for these cancers is in the pleural cavity (the space between the lungs and chest wall). Mesotheliomas can also be found elsewhere in the body, such as in the liver, intestines, or stomach tissues.

How is a Malignant Mesothelioma

Malignant epithelioid mesothelioma (MEM) is a malignant subtype of epithelioid mesothelioma.

There have been a number of case reports of MEM. The first case report was in 1998 by White, et al., and the first review of all cases was published in 2006.

The American Journal of Gastroenterology published a review in January 2009 that included 57 cases from 16 different countries and 12 reviewed articles. MEM is usually detected at early stages, usually before metastasis would develop, so the median survival time for these patients is about 5–10 years. It is often misdiagnosed as malignant pleural mesothelioma (also called mixed mesothelioma), but to be diagnosed correctly, it should be differentiated from malignant ascites mesothelioma or pleural adenopathy due to sarcoidosis (called “chronic malignant ascites” or CMA).

Symptoms and Treatments of an Epithelioid Mesothelioma

Malignant epithelioid mesothelioma (MET) is the most common type of cancer found in the pleural effusions of people with cirrhosis. The term ‘mesothelioma’ is used to describe this type of cancer, which arises in the mesothelial cells lining the pleural space. Cancer cells are usually proliferative and can invade various parts of the body, including the lung and liver. Metastases from MET can be difficult to treat because they often spread rapidly throughout the body. Numerous studies have shown that cigarette smoke, asbestos exposure, or occupational exposure to asbestos is associated with MET development.

Symptoms of Epithelial Cell Mesothelioma

The epithelioid mesothelioma is a malignant tumor of the lung which is often referred to as the “sailor’s lung”. This rare cancer forms in undifferentiated squamous cells of the bronchial and bronchiolar alveoli, where it may be confused with other benign and malignant tumors. Two major risk factors for epithelial cell mesothelioma are smoking, asbestos exposure, and pregnancy. However, most commonly this disease is caused by cigarette smoke exposure either through direct inhalation or through exposure to secondhand smoke.

The prognosis for Epithelial Mesothelioma

Epithelial mesothelioma is a rare malignant tumor, typically found in the pleura, peritoneum, lung lining, and lining of the blood vessels. The malignant nature of the epithelioid mesothelioma makes it hard to diagnose.

The tumor is usually diagnosed when its size exceeds 2 cm in diameter or when there are at least 10 lesions on any part of the body. There is no specific treatment for epithelial mesothelioma, but patients with this disease generally have a good prognosis.

Epithelial Mesothelioma Diagnosis

Epithelial mesothelioma is a rare malignant tumor of the mucous membrane lining the gastrointestinal tract. It is usually found in children, young adults, and older adults. There are at least 8 to 10 different types of epithelial mesothelioma and they are divided into 2 subtypes:

  1. Type I tumors (also called “non-invasive” or “asymptomatic”) occur in the chest wall and lung, lungs, cervix, abdomen, ovary, kidney, or pelvis.
  2. Type II tumors (also called “invasive” or “symptomatic”) occur in the abdomen, skin, lymph nodes, or bones.

Role of Immunotherapy in Diagnosis

The role of immunotherapy in the diagnosis of malignant epithelioid mesothelioma (MEDM) is a topic that has been debated for decades, with various opinions on the effectiveness and safety of various types of immunotherapy in cases when one or more of the following criteria is present:

  • 1. The tumor’s primary site is a lung or a peritoneal cavity, such as the peritoneal cavity.
  • 2. The tumor has a hemopoietic or lymphatic origin.
  • 3. The tumor has metastases to other organs or tissues within the body, such as the brain, liver, spleen, and/or lymph nodes, which are histologically normal at the time of diagnosis; however, their presence may make the patient more susceptible to secondary infections and tumors locally at other sites within the body (e.g., pleural effusion).
  • 4. The tumor has an unusual morphologic appearance (e.g., unusual location within an organ or tissue) that may make it difficult to diagnose on clinical grounds alone; however, such tumors also require histopathological confirmation in order to confirm their presence and histology typically can be performed only after surgical excision; therefore, even if tumors do not have readily identifiable features that would require surgical excision for localization by histopathology alone, some tumors may have such features (e.g., tumor cells with “forked” nuclei) that does not allow easy localization-based solely on clinical grounds alone.
  • 5. Tumors with high expression levels of CD30 or CD56 are overexpressing receptors that bind to T-cell receptors (TCRs), indicating a poor prognosis for patients diagnosed with MEDM; however, this condition is rare and there is no evidence suggesting a link between CD30 and prognosis in patients with MEDM when compared to patients without such overexpressing receptors but diagnosed with MEDM through clinical criteria alone (i.e., no evidence showing that overexpression of any TCR gene results in poor prognosis); therefore, this type of tumor is generally considered benign when compared to other types of cancers; thus it may be difficult for physicians to distinguish between benign and malignant tumors based solely on clinical criteria alone in cases where tumors express high levels of any surface markers using reverse transcription-polymerase chain reaction (RT-PCR).

Epithelial Mesothelioma Cell Subtypes

Epithelial mesothelioma is a rare and often fatal cancer of the lining of the lung and pleural cavity.

The term epithelioid mesothelioma was coined by Howard C. Hughes to refer to an unusual type of tumor seen in individuals with a history of cigarette smoking. Mesotheliomas are generally benign tumors that arise from the lining of the lungs, most commonly from the trachea, bronchi, and bronchioles. An estimated 90% of all lung tumors are epithelioid mesothelioma; approximately 5% are malignant and other types include papillary carcinoid tumors, SCCA-like tumors, and hilar adenocarcinomas.

While it is possible for individuals to have only one type of epithelial mesothelial tumor (e.g., papillary carcinoid or SCCA-like), most patients have multiple types present at different points in time.

Epithelial Mesothelioma Treatment Options

Epithelial mesothelioma (EMT), is a rare but aggressive cancer that originates from the lining of the body sacs, or pleura. It can be found in the lungs, abdomen, and pelvis. The average life expectancy for EMT is 18-24 months (1). When diagnosed, the prognosis is usually good with early treatment (1).

It was first described in 1938 by German pathologist Hans Kienast who found it in mice and later confirmed its presence in humans (2).

The initial treatment for EMT is surgery to remove the cancerous condition from the lungs or abdomen of patients suffering from this type of cancer. This incision can be either laparoscopic or open. Though surgery may result in recovery times between up to two years, many patients find that they can survive longer than expected on chemotherapy as well as radiation therapy alone (3).

Conclusion: Epithelial Mesothelioma

Mesothelioma is the most common cancer in the world. By some estimates, it is responsible for more deaths than any other type of cancer (1,000-2,000 per year). This even includes cancers that are usually only found incidentally and may not be considered malignant at all.

Epithelial mesothelioma occurs when there are abnormal regions in the mesothelium (the outer lining of the organs).

In addition to causing pain and difficulty breathing, epithelial mesotheliomas can cause significant health problems for their victims. It can also lead to a slow death over many years. The prognosis is poor if a tumor does not spread to other parts of the body.

The exact reasons for epithelial mesothelioma are not well understood; however, it generally does not occur at sites where there is high immune tolerance (such as in areas of the brain), as well as at sites that would normally be protected by high levels of special antibodies against epithelial cells. Instead, it tends to occur in areas with low tolerance and immunological resistance such as bones and joints; or where there are other risk factors such as smoking or liver disease.

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