Mesothelioma diagnosis is difficult as the symptoms are similar to a number of other illnesses
A mesothelioma diagnosis often begins with a review of the patient’s medical history. A history of exposure to asbestos may increase clinical suspicion for mesothelioma. A physical examination is performed, often followed by chest X-ray and lung function tests. The X-ray may reveal pleural thickening commonly seen after asbestos exposure and increases suspicion of mesothelioma. If the chest X-ray reveals abnormalities, follow-up CT (or CAT) scan or an MRI is usually performed.
If a large amount of fluid is present, abnormal cells may be detected by cytology if this fluid is aspirated with a syringe. For pleural fluid this is done by a pleural tap or chest drain, in ascites with an paracentesis or ascitic drain and in a pericardial effusion with pericardiocentesis. While absence of malignant cells on cytology does not completely exclude mesothelioma, it makes it much more unlikely, especially if an alternative diagnosis can be made (e.g. tuberculosis, heart failure).
If cytology is positive or a plaque is regarded as suspicious, a biopsy is needed to confirm a diagnosis of mesothelioma. A doctor removes a sample of tissue for examination under a microscope by a pathologist. A biopsy may be done in different ways, depending on where the abnormal area is located. If the cancer is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor makes a small cut through the chest wall and puts a thin, lighted tube called a thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look inside the chest and obtain tissue samples.
If the cancer is in the abdomen, the doctor may perform a laparoscopy. To obtain tissue for examination, the doctor makes a small opening in the abdomen and inserts a special instrument into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.
Mesothelioma Staging And Outcomes
Once a diagnosis of mesothelioma is confirmed, staging of the disease often remains difficult and can be an obstacle to effective treatment. Staging techniques are based on knowledge about where the tumor is located, how extensive it is and whether it is still locally contained or whether it has metastasized to organs or adjacent tissues.
Since staging is essential to selecting the appropriate treatment, much effort has been invested in developing an accurate pre-operative staging technique.
The newest mesothelioma staging system is the Brigham system, which was developed at the Dana-Farber Cancer Institute/Brigham and Women’s Hospital Thoracic Oncology Program, after analyzing the first 52 patients treated with trimodality therapy. The Brigham facility is the location of the International Mesothelioma Program, headed by Dr. David J. Sugarbaker.
This staging scheme allows four stages and considers resectability and nodal status. Patients with stage I disease have resectable tumors with no affected lymph nodes. Stage II refers to resectable tumors accompanied by positive lymph nodes. Stage III includes tumors that are unresectable due to local extension into mediastinal structures or through the confines of the diaphragm. Stage IV describes metastatic disease at presentation.
Brigham Staging System for Malignant Pleural Mesothelioma
- Stage I – Disease confined to within capsule of the parietal pleura; ipsilateral pleura, lung, pericardium, diaphragm, or chest-wall; disease limited to previous biopsy sites
- Stage II – All of Stage I with positive intrathoracic (N1 or N2) lymph nodes
- Stage III – Local extension of disease into chest wall or mediastinum, heart, or through diaphragm, peritoneum; with or without extrathoracic or contralateral (N3) lymph node involvement.
- Stage IV – Distant metastatic disease
The Brigham system incorporates elements of the commonly accepted mesothelioma staging guidelines set forth by the International Mesothelioma Interest Group (IMIG), which also is based in part on the (N) descriptors adopted by the International Lung Cancer Staging System (AJCC). This system is referred to as the TNM based staging system.
- T or tumor staging – what is the size and location of the primary tumor in relation to nearby organs and structures?
- N or nodal staging – are lymph nodes positive or negative for meso?
- M or metastatic staging – is there evidence of metastasis?