One of the first physical examinations to be conducted is the examination of fluid from the chest or abdomen. Fluid extractions from the chest via needle (thoracentesis) are performed for two reasons, to relieve the buildup of fluid and to provide a sample for a cytological examination. Unfortunately, examinations of the pleural effusion or abdominal ascites are only rarely conclusive. A negative result is inconclusive as enough viable cells may not have been extracted a positive results will define a malignant process but further examination is warranted.
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Biopsies during the Mesothelioma Diagnosis Process
The principle means of obtaining a pathology specimen is through surgery and in most cases this involves a VATS procedure (video assisted surgery). For pleural mesothelioma, the surgery itself is called a thoracotomy (chest incision) followed by a thoracoscopy (fiber optic exam of the chest). For abdominal biopsies the surgery is called a laparotomy and laparoscopy (fiber optic exam of the abdomen). These procedures are in themselves difficult surgeries that are only offered in the event a serious illness is suspected. Since the symptoms of mesothelioma are often confused with other, more benign, illnesses, many people either don’t receive them or receive them only after long delays, affecting the prognosis of their cancer.
In an attempt to improve diagnosis of lymph node involvement, some institutions will require a mediastinoscopy to biopsy the lymph nodes in the chest. This procedure is day surgery and a finding of positive lymph nodes might influence a decision not to offer surgery since the surgical staging would be at least stage 3.
Diagnostic examinations may or may not involve rudimentary mesothelioma treatment attempts. In pleural cases, many surgeons opt to perform a pleurodesis. . The purpose of this is to irritate the site and stimulate the formation of scar tissue which wall off the space thus preventing accumulation of fluid. If the fluid accumulation isn’t stopped, it leads to secondary problems such as pneumonia, or compression of key blood vessels and arteries. Untreated, the fluid accumulation may lead to serious and life threatening complications long before the tumor itself is fatal. It is recommended that this procedure not be performed prior to a consult with a pleural mesothelioma specialist, unless it is deemed absolutely necessary, as it may preclude some innovative treatment options that are being offered at mesothelioma treatment centers. Further discussion can be found in the section labeled chemotherapy.
After the thoracotomy, the surgeon will temporarily insert a tube, placed in the opening and sewn air-tight to the skin, to allow the remaining fluid and blood from the surgery to drain. An alternative to a pleurodesis would be the placement of a pleurex catheter which permits drainage of pleural fluid and can be managed at home or in the hospital setting. This is used as a palliative procedure to manage effusions and ascites. Chest tubes or chest ports are inserted and used for instillation of intra pleural chemotherapy.
The Role of Blood Cell Count in a Mesothelioma Diagnosis
Nonspecific laboratory findings in patients with malignant mesothelioma can include an elevation in the white blood count, number of platelets, erythrocyte sedimentation rate and a decrease in red blood cells (anemia). Elevations of CA125 and hyaluronic acid are also noted in many cases of mesothelioma. All of these findings are nonspecific and are not reliable for making the diagnosis of mesothelioma nor following response to therapy.
Confirming the Diagnosis
Pathology; once a biopsy is obtained, special stains are necessary to confirm the diagnosis of mesothelioma. Positive staining for Calretinin, WT1 and cytokeratin is desired, as well as negativity for CEA, CD15, TTF-1 and B72.3. The utility of these stains assists in distinguishing mesothelioma from other cancers that present in similar fashion for example lung cancer. Despite advances in making a pathological diagnosis rare subtypes, poorly differentiated mesotheliomas, and sarcomatoid continue to present diagnostic challenges. Electron microscopy can be employed to look for specific characterizes of the cell in some of these more challenging cases.
Selected articles for further reading are listed below:
Significance of combining detection of E-cadherin, carcinoembryonic antigen, and calretinin in cytological differential diagnosis of serous effusion][Article in Chinese]
