Biopsy
In addition to the physical examination and radiographic tests, a biopsy is necessary for the confirmation of a diagnosis of mesothelioma. For a biopsy, a surgeon or a medical oncologist (a physician who specializes in diagnosing and treating cancer) obtains a sample of tissue from the body for examination under a microscope by a pathologist. A biopsy is performed in different ways, depending on the location of the tissue to be removed. Sometimes, a patient will undergo more than one biopsy procedure.
Sometimes a sample may be taken of the fluid that builds up around the mass in a procedure called a thoracentesis.
Tissue samples can be obtained through a needle biopsy, in which cells are extracted through a long needle; a tissue biopsy, using a very small incision; or a more open surgical biopsy, which experts now think may provide the most reliable means of diagnosing mesothelioma.
Other biopsy procedures may be used after diagnosis to determine how far the cancer has spread.
After a biopsy is performed, the tissue obtained is sent to experts for an evaluation to determine if mesothelioma is present. If fluid is removed during a thoracentesis or thorascopy, the fluid is sent to a Cytology lab for analysis. A tissue biopsy will be sent to a surgical pathology lab for analysis. The same is true when an entire tumor, pleura or lung is surgically removed. After analysis is completed, small pieces of any remaining tissue are preserved in paraffin wax for future use. Regardless of where the biopsy material is sent, the patient’s physician will receive a written report of the results. The doctor may receive an oral report from the lab prior to the written results.
Analysis of the biopsy material will be conducted by a pathologist, a doctor who specializes in identifying and determining the cause of diseases. A pathologist is trained to analyze abnormal cell growth, which can reveal the presence of mesothelioma, and other diseases.
Ordinarily, the pathologist will remove a razor thin layer of tissue from the sample, set the tissue on a microscope slide, add dye to the slide to make the cells more visible, and then seal the slide so it can be viewed under a microscope. It is often difficult to diagnose mesothelioma just by looking at the cells in the fluid taken from around the lungs, abdomen, or heart, or even from the tissue obtained in a small needle biopsy. Under the microscope, mesothelioma can have the appearance of several other types of cancer. Pleural mesothelioma, for example, may look like some types of lung cancer and peritoneal mesothelioma may seem to be a cancer of the ovaries. For this reason, special laboratory tests are often performed on the biopsy tissue to help distinguish mesothelioma from another type of cancer.
These tests often use special techniques to locate certain types of chemicals (called “markers”) contained in mesothelioma tumors. One method, immunohistochemistry, looks for certain proteins on the surface of the cells. This test can be used to tell the difference between mesothelioma and lung cancer, which can appear to begin in the lining of the chest cavity. DNA Microarray analysis is a newer test. This method actually analyzes genes in the tumor. Mesothelioma has different gene patterns than other types of cancers.
The electron microscope is also used to analyze biopsy samples and help diagnose mesothelioma. This microscope can magnify samples more than one hundred times greater than the traditional light microscope that is generally used in cancer diagnosis. The more powerful microscope enables doctors to see the small parts of the cancer cells that make mesothelioma different from other types of cancer.
A biopsy is not only useful for the pathologist who diagnoses a patient’s mesothelioma; a biopsy also allows the patient’s oncologist to analyze the possible spread of cancer cells to other parts of the body. When a complete tumor is removed from the body, the pathologist carefully examines the edges, or “margins,” of tissue outside the tumor to see if cancer is present. A finding of “negative margins” means the cancer has probably not spread; the appearance of “positive margins” suggests that the surgeon did not completely remove the cancer. Mesothelioma spreads quickly, so oncologists commonly order additional tests, including biopsies and x-rays on parts of the body that are commonly affected, such as the lymph nodes. The mediastinoscopy is one such test.
Thoracentesis
Some mesothelioma patients develop fluid in their lungs. This is called a pleural effusion. Often, a doctor will take a sample of this fluid with a needle injected into the chest and test the fluid for cancer cells. The procedure might also be performed for draining fluid from the lungs to help relieve pain. Although the procedure is safe and quick, its sensitivity is unfortunately less than 50 percent, and a negative test is generally not sufficient to rule out mesothelioma.
Needle Biopsy
A patient suspected of having mesothelioma will often be given a needle biopsy at the start. For this procedure, the doctor uses a long, thin needle to take samples of cells from the chest, or from the abdomen or pericardial region for examination under a microscope. This test can be uncomfortable but may take only a few minutes. Small pieces of the tissue are taken and then sent to a laboratory for analysis.
The doctor might also use an x-ray, CT scan or fluoroscopy to guide the needle as it is inserted into the tumor. Fluoroscopy is a diagnostic procedure in which x-rays are passed through the body and then projected onto a screen, providing a continuous image of the body’s internal structures.
Tissue Biopsy
Alternate biopsy procedures involve a small incision through which a surgeon can operate a tiny telescope and other fine instruments to obtain a tissue sample. Fluid can also be collected during such procedures. These procedures, called thoracoscopy and laparoscopy/peritoneoscopy, are done in the hospital under general anesthesia.
Thoracoscopy
A thoracoscopy permits a surgeon to look inside the patient’s chest. The procedure is sometimes called a VATS (video-assisted thoracic surgery) pleural biopsy. The surgeon makes one or two small incisions between the ribs and inserts a tube with a tiny video camera into the chest cavity. The doctor uses special forceps to remove the tissue sample as the tumor is viewed on a monitor screen connected to the telescope (the thoracoscope). The surgeon take special care to make the incisions in a place on the chest where they can be incised given that cancer cells can contaminate any incision.
Laparoscopy/Peritoneoscopy
A laparoscopy is similar to a thoracoscopy, in that it allows the surgeon to view and obtain a biopsy of a peritoneal tumor. The laparoscopy may also be referred to as a peritoneoscopy. In a laparoscopy, a video camera placed on a flexible tube is injected into the abdominal cavity through small cuts to the front of the abdomen. The biopsy specimen is sent to the pathology laboratory for examination and interpretation by the pathologist. If the procedure fails to yield enough tissue for the pathologist’s study, however, more extensive diagnostic surgery may be necessary.
Surgical Biopsy
Recently, mesothelioma doctors have determined that the open lung biopsy is the most reliable in making an accurate diagnosis. The procedure is a form of surgery and is done in the hospital under general anesthesia. The types of surgical biopsy are called thoracotomy and laparotomy.
Thoracotomy
A thoracotomy is a type of surgery to open the chest between the ribs to allow a surgeon to check for signs of disease. Sometimes, the surgeon will remove just a sample of tissue for testing. Other times, a larger portion of tumor is removed or, possibly, the entire tumor. The tissue will be forwarded to a pathologist for review and the patient’s physician will receive the report at a later time. A chest tube may be left in place for a few days after surgery to prevent the lung from collapsing.
Laparotomy
A laparotomy is surgery to open the abdomen to permit a physician to inspect for signs of peritoneal mesothelioma and to remove a sample of tissue for testing. As with a thoracotomy, the tissue sample is sent to a pathologist for analysis and the patient’s doctor is given the results at a later date.
Other Biopsy Procedures
Some biopsies are performed not just to confirm the diagnosis of mesothelioma, but also to discover the extent to which a mesothelioma tumor may have spread in the body. These biopsies include the mediastinoscopy and the bronchoscopy. This information is important for staging the cancer—that is, determining how advanced the cancer is. This information in turn assists the physician and the patient in choosing appropriate treatment options.
Mediastinoscopy
A mediastinoscopy is done to learn whether an existing tumor has spread to the mediastinal nodes (the lymph nodes in the center of the chest). A mediastinoscopy involves inserting a lighted tube (mediastinoscope) under the chest bone at the level of the neck and moving the scope down into the chest. This allows the surgeon to view the lymph nodes in this area and to take samples to check for malignant mesothelioma. The mediastinoscopy is performed under general anesthesia with the patient completely asleep.
The lymph nodes are described as bean-sized collections of cells that help the body fight infections and cancers through the immune system. Lymph nodes exist everywhere in the body and act to filter out infection and tumor cells. Cancers in the lung commonly spread to the lymph nodes, but for mesothelioma, this is less common. Tests on sample lymph nodes taken during a mediastinoscopy, then, may help distinguish lung cancer from mesothelioma. In addition, the tests may reveal whether a cancer is still localized or has begun to spread. This determination is important because disease treatment will vary according to the status of the lymph nodes.
Bronchoscopy
If it is suspected that a patient has pleural mesothelioma, the doctor may also perform a bronchoscopy. In this procedure, a flexible lighted tube is inserted through the patient’s mouth, down the trachea, and into the bronchi to determine whether any other masses are present in the airway. Small samples of tissue that appears abnormal may be removed for analysis by a pathologist.