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Pathology is the science of disease cause and effects. A pathologist studies diseases but can also help diagnose diseases, especially by examining tissue samples in a laboratory setting. Pathologists also examine scanned images and blood of a person who might have mesothelioma. After studying these he or she can offer an informed opinion or contribute to a diagnosis.
Different diseases, and even different types of cancer, leave telltale signs in a person’s body. These signs are often observed in the symptoms a person experiences or in the blood and cells of the patient. The pathology of mesothelioma is a crucial part of an accurate diagnosis.
The Pathology of Tumor Growth
Observing the anatomy of a particular cancer, or how the tumors grow and develop, is one way of diagnosing mesothelioma. The most obvious anatomical sign of mesothelioma is the thickening of the pleural space, the lining of the lungs. Additionally, the tumor may develop small nodules over the surface of the pleura and other similar areas including the diaphragm.
Pathologists have described rare cases of localized malignant mesothelioma. This presents as a single mass rather than the characteristic pleural thickening and nodules.
The common nodules characteristic of mesothelioma usually range in size from one millimeter to one centimeter. As the cancer advances, the nodules and tumors form plaques. Plaques develop into thick tissue that encases and interferes with organs, usually the lungs.
Metastasis, or the spread of cancer cells from the primary location, is another sign of advanced mesothelioma. With pleural mesothelioma, the cancer often spreads to skeletal muscle in the chest cavity. It can also spread to deep layers of the skin, the diaphragm, organs of the abdominal cavity, and the lymph nodes. In peritoneal mesothelioma, the tumor often spreads to the liver, spleen, intestines, and other abdominal organs.
Histology: Pathology of Cells
Pathologists examine macrostructures, but also microscopic structures like cells. Mesothelioma is difficult to diagnose by examining the macrostructure of the tumor. Examining the cells is also important. However, careful cell examination doesn’t guarantee proper identification of cancer cells.
A biopsy is necessary for complete and accurate diagnosis. Cells are extracted from the tumor and examined under a microscope for characteristic signs of mesothelioma. Pathologists use specific stains to identify chemicals and structures within and on the surfaces of cancer cells from the biopsy sample. There are four distinctive cell types that may be found in tissue from a mesothelioma tumor:
- Cells that may be cube, oval, or polygonal and mimic non-cancerous cells of the mesothelium. This accounts for most cases of mesothelioma and is one reason diagnosis is difficult.
- Cells shaped like spindles that mimic those in lung cancer. This is yet another reason mesothelioma is difficult to diagnose.
- In biphasic mesothelioma tumors, there are both types of cells.
- Cells that resemble those found in a condition called fibrous pleuritic. Distinguishing between the two is very difficult.
Cytology is the study of cells. This science requires a less invasive biopsy. A simple needle biopsy is usually adequate. Cells are then examined to determine if malignant cells are present. The technique is quick and inexpensive. However, this method cannot determine if a malignancy is the original tumor or one that spread from the original location. Confirmation of cancer with cytology is usually followed by a more extensive histology study.
Cytology tests often look for large balls of cells that resemble the structure of a berry. Cells in these bundles are usually larger than those in healthy tissues. Atypical features in the nucleus of a cell are also characteristic of mesothelioma. There may also be structures called macronulcleoli.
Pathologists can also use immunohistochemistry to identify cancer cells of the mesothelium. This is one of the most accurate ways to distinguish between mesothelium cancer cells and other types of cancers. Immunohistochemistry uses antibodies to detect the antigens that are characteristic of a particular type of cancer cell.
To see the antibodies, samples are typically stained or attached to fluorescent dye. As the antibodies attach to antigens specific to mesothelioma, they become visible under these conditions. If they do not attach, the stain or dye is not activated, and the presence of mesothelioma is not confirmed. An immunohistochemistry test is often required in legal cases of asbestos-related mesothelioma to confirm the diagnosis.
Pathology is important to the study of all diseases. This science aids proper diagnosis but also adds to our understanding of how diseases like mesothelioma progress. Understanding how a disease progresses and affects the body helps doctors form better treatment options. For someone with mesothelioma, pathology techniques help make more accurate diagnoses. This cancer is already difficult to pinpoint, so detailed pathology helps make early and accurate diagnoses, which is critical for effective treatment.
Page Edited by Patient Advocate Dave Foster
Dave has been a mesothelioma Patient Advocate for over 10 years. He consistently attends all major national and international mesothelioma meetings. In doing so, he is able to stay on top of the latest treatments, clinical trials, and research results. He also personally meets with mesothelioma patients and their families and connects them with the best medical specialists and legal representatives available.