Pathology can involve anatomical studies of the appearance of the disease in tissues, the way it progresses, and the study of how the disease affects cells on a microscopic level.
Fast Fact: Pathologists
provide crucial information for mesothelioma diagnosis, including the
extent of disease progression, surgical resection margins and if the
cancer has spread to the lymph nodes.
Anatomical Pathology
Pathologists note certain physical characteristics of
asbestos-related tumors. The majority of these tumors affect the pleura
(75 percent) and the peritoneal cavity (10 to 20 percent). Only rarely
do they affect the pericardium (1 percent) and tunica vaginalis (less than 1 percent).
One of the most unique pathological features of these diseases is that the cancer forms in the mesothelial cells in the linings of organs and grows in a diffuse pattern. This growth pattern causes the tumors to spread and form tiny nodules across the surface of the outer lining of the lungs (pleura) or abdomen (peritoneum). Localized malignant mesotheliomas are extremely uncommon, though a few cases have been reported. These localized tumors are more easily removed in surgery and therefore have a much better prognosis.
In its early stages, diffuse pleural mesothelioma
begins as multiple tumor nodules on either or both of the visceral and
parietal pleural surfaces. The nodule size ranges from 1 mm to 1 cm. As
the disease progresses, the tumors form plaques. Eventually, these
tumors can form a rind around the organ, constricting it and interfering
with its normal functions. Organ encasement is usually a sign of
advanced disease. After tumors begin to encase organs, the visceral and
parietal linings in pleural, peritoneal and pericardial mesothelioma typically adhere together.
Pleural cancers often spread to skeletal muscle in the chest wall and may also invade the skin and subcutaneous tissue (deepest layer of skin). Tumors can also invade the hemidiaphragm and spread into the abdominal cavity. When present in the pleural cavity, the tumors can also invade biopsy tracks, surgical incisions and the fissures of the lung. At very late stages, they metastasize into the hilar lymph nodes, which are located in the chest close to where the bronchi enter the lungs.
One of the most unique pathological features of these diseases is that the cancer forms in the mesothelial cells in the linings of organs and grows in a diffuse pattern. This growth pattern causes the tumors to spread and form tiny nodules across the surface of the outer lining of the lungs (pleura) or abdomen (peritoneum). Localized malignant mesotheliomas are extremely uncommon, though a few cases have been reported. These localized tumors are more easily removed in surgery and therefore have a much better prognosis.
Pathological Characteristics of Disease Progression
Stage I
Cancer is localized. Surgery may be able to remove tumors and prognosis is highest.Stage II
Cancer has spread beyond point of origin. Surgery may still be an option, but life expectancy is decreased.
Stage III
Cancer has progressed to advanced stage of development. Palliative treatments to ease symptoms may be considered.Stage IV
Cancer has spread to distant locations. Palliative treatments can improve comfort, but life expectancy is severely decreased.
Pleural cancers often spread to skeletal muscle in the chest wall and may also invade the skin and subcutaneous tissue (deepest layer of skin). Tumors can also invade the hemidiaphragm and spread into the abdominal cavity. When present in the pleural cavity, the tumors can also invade biopsy tracks, surgical incisions and the fissures of the lung. At very late stages, they metastasize into the hilar lymph nodes, which are located in the chest close to where the bronchi enter the lungs.
Fast Fact: Patients are rarely treated for cancer with chemotherapy unless there is a pathological diagnosis.
In advanced peritoneal mesothelioma,
the bowel is often encased by tumors, and the liver and spleen may also
be encased. Tumors that originate in the pericardium are rare, but the
same diffuse spread pattern is also observed and it often infiltrates
the muscle tissue of the heart (myocardium).
Cellular Pathology
While the anatomical characteristics of a tumor can help diagnose a type of cancer, most tumors require a pathologist to study the types of cells present in a malignant growth. Using a microscope, pathological studies differentiate mesothelioma cells from other types of cancer and are used to diagnose specific subtypes of the disease through two methods: histology and cytology.Histopathologic Features
Histology involves the use of tissue samples obtained through a biopsy.
Histopathology specifically refers to the study of the cells in
diseased tissue. For mesothelioma, actual tissue from tumors is usually
obtained through an incisional/core or excisional biopsy.
Mesothelioma Histology Tissue Stain
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