Histopathology and Epithelioid Mesothelioma
Histopathology and Epithelioid Mesothelioma
Histopathology is a field of pathology specializing in the microscopic study of diseased tissue. Histopathological examinations are used to accurately diagnose diseases like malignant mesothelioma.
The diagnosis of malignant mesothelioma typically begins with a patient visiting a doctor with symptoms mirroring viral pneumonia (chest pain, chronic cough, respiratory distress). Most patients complain of chronic chest pain, requiring their doctor to request an x-ray or CT scan of the chest. A fluid buildup in the chest known as pleural effusion is the first indicator that a patient may be suffering from diffuse malignant mesothelioma. To verify this preliminary diagnosis, a sample of suspect tissue is surgically removed (biopsy) and delivered to a histopathologist for detailed examination.
The removed tissue is placed in a fixative solution designed to prevent its decay. The most commonly used histopathological fixative is formalin, a solution that is 10% formaldehyde in water. After being placed in a fixative, the tissue sample undergoes a series of steps designed to embed it, transforming the moist and soft tissue into a hard paraffin block. Once embedded, the tissue sample can be sectioned into very thin slices using a device called a micrometer.
Once sectioned, the tissue is almost ready for microscopic examination. The final preparative step involves "staining" the section with pigments (hematoxylin and eosin) in order to make the near-transparent section viewable under the microscope. Examination of the sectioned tissue will allow for an accurate diagnosis of malignant mesothelioma cell type.
Epithelioid Mesothelioma
Malignant mesothelioma cells come in three types: epithelioid mesothelioma, sarcomatoid mesothelioma and biphasic mesothelioma.
Epithelioid cancer cells are the most common of the mesothelioma cells, accounting for 50% to 70% of all malignant mesothelioma cancer cells. Epithelioid cancer cells combine a uniform shape with a tubular array to create a unique cellular pattern. During histopathological examination, the nucleus of an epithelioid cancer cell is clearly visible under high magnification.
Sarcomatoid mesothelioma cancer cells are the least common of the mesothelioma cells. The irregular oval shape of sarcomatoid mesothelioma cells is somewhat common for cancer cells, making it difficult to differentiate them from more typical sarcoma cancer cells.
Biphasic cancer cells are a combination of epithelioid and sarcomatoid mesothelioma cells. Biphasic cell groupings can either be mixed together or separated into two distinct sections.
Epithelioid Mesothelioma and Adenocarcinoma
Carcinoma is a type of cancer that originates in specialized tissue serving as lining throughout the body (epithelium). Adenocarcinoma is a type of carcinoma that originates in the inner epithelium of an organ. When adenocarcinoma forms in the lining of the lungs, it can spread to the lung cavity (pleura), where it can be mistaken for epithelioid mesothelioma.
Both adenocarcinoma and epithelioid mesothelioma develop from the epithelium and therefore have a similar cellular appearance. Chemical staining (histochemistry) of adenocarcinoma and epithelioid mesothelioma can occasionally yield similar results, and symptoms of the two diseases tend to mirror one another; the result is that adenocarcinoma and epithelioid mesothelioma are commonly misdiagnosed.
Epithelioid mesothelioma patients have an average survival time of 8.5 months. Traditional treatments for mesothelioma have been unsuccessful in battling cases of epithelioid mesothelioma. New mesothelioma treatments are in the process of ongoing research, development and testing.