Diagnosis of Pleural Mesothelioma
The initial examination
The first stage is the patient’s attendance at his General Practitioner with symptoms. The symptoms are usually shortness of breath and/or pain in the chest. The doctor will take a history of the symptoms and perform a physical examination.
In his initial examination the doctor will be looking for signs of weight loss (cachexia), and reduced chest expansion. The doctor is likely to tap the chest with their fingers and listen to the sound produced (called percussion: a stony dullness will be present if there is significant pleural fluid and thickening). The doctor will also use a stethoscope to listen for breath sounds (called auscultation). Breath sounds may be reduced or absent or sounds may be abnormal, if a significant lung condition is present.
The plain chest x-ray plays an important role in the early diagnosis of mesothelioma. Around 70% of patients will have a pleural effusion detectable on a chest x-ray. Pleural thickening may also be present. Review of old x-rays (if any are available) will be important to look at changes over time. The need for a referral to a chest physician will be based on both the radiological and clinical findings.
CT of the pleura
Contrast enhanced CT (computed tomography) scanning is an essential next step in establishing both the diagnosis and assessing the stage of the disease. CT scans and HR CT scans (high resolution CT scans) are more sensitive and specific than chest x-rays in diagnosis.
CT scans can help differentiate benign from malignant disease. Indicators of pleural mesothelioma include circumferential pleural thickening and nodular pleural thickening.
There is no need to drain pleural fluid prior to the CT scan.
Pleural fluid Cytology and needle Biopsy
Tissue confirmation of diagnosis is very important. The first step is often a needle drainage of the pleural effusion. This may take place with or without a biopsy (obtaining a tissue sample).
To achieve the best chance of cytological diagnosis it is important to obtain an adequate amount of well preserved fluid, which has to be prepared to ensure satisfactory cell concentration suitable for making quality smears and cell blocks.
It has been shown in a number studies that cytology (examination of the pleural fluid) is of only limited diagnostic value. The results obtained from cytology alone are often unreliable or inconclusive.
Histopathological (Biopsy of lung tissue) diagnosis of Mesothelioma
Histopathology is the study of cell structure. Histopathology of mesothelioma is the conclusive diagnosis (in conjunction with clinical, radiological and surgical findings).
The most reliable method of obtaining sufficient tissue to make a histological diagnosis of mesothelioma is surgical biopsy. In many cases thoracoscopy is the preferred method of surgical biopsy. The procedure involves using a lighted scope with a camera, to look inside the chest cavity. Thoracoscopy involves direct sight of the pleural surfaces and consequently allows targeting of abnormal areas where biopsies are taken. Thoracoscopy can be performed under local anaesthetic. Thoracoscopy offers a high rate of success for diagnosis of mesothelioma. Local anaesthetic thoracoscopy is now a standard investigation in suspected pleural mesothelioma. British Thoracic Society (BTS) guidelines recommend thoracoscopy as part of the procedure when pleural effusion is present.
The diagnostic accuracy of biopsies obtained at thoracoscopy is far superior to that of a needle biopsy. Thoracoscopy provides visualisation of pleural cavity and good quality biopsy samples, with often numerous biopsies taken from multiple sites. Once satisfactory biopsies are obtained tissue samples must be looked at under the microscope in the laboratory.
Diagnosis of Peroniteal Mesothelioma
Peritoneal Mesothelioma is a difficult cancer to diagnose. It presents in an area of the body where other disease process can be suspected. It often takes months from the initial presentation of symptoms to the initial diagnosis. This delay in diagnosis combined with the aggressive nature of mesothelioma tumours, often results in a late stage diagnosis for patients.
As with pleural mesothelioma the diagnostic process begins with a thorough examination of the patients medical history and physical condition, followed by CT-scans and x-rays. A history of exposure to asbestos should alert doctors to the possibility of mesothelioma cancer.
X-rays and CT scans are useful in diagnosis, but only a biopsy can confirm a peritoneal mesothelioma diagnosis. A biopsy is a surgical procedure that involves the removal of fluid and/or tissue samples from areas of the peritoneal and these samples are tested in the laboratory. As with pleural mesothelioma there are a number of surgical procedures available for peritoneal mesothelioma. A common surgical procedure used to reduce fluid, swelling and pain in the abdomen is a paracentesis. This is the insertion of a thin needle or tube into the abdomen to remove the fluid from the peritoneal cavity. It is often accompanied with a biopsy which is used to make the diagnosis of peritoneal mesothelioma.
A second form of surgery for peritoneal mesothelioma is cytoreductive surgery. In this procedure as much of the cancer as possible is removed. During the operation chemotherapy is given straight into the peritoneal cavity. Research has suggested that the chemotherapy works better if its heated to a few degrees above body temperature first. This procedure is called hypothermic intraoperative introperitoneal chemotherapy (HIIC). Chemotherapy into the abdominal cavity may be repeated a few times after the surgery.
Cytoreductive surgery is only possible for patients who are very fit and who have early stage mesothelioma. Before the surgery is undertaken the patient will have a very thorough examination to stage the mesothelioma and to ensure that the patients general health is up to the major surgery.
A peritonectomy is a surgical procedure which involves the removal of the peritoneum, and all gross primary cancer observed, together with removal of all or part of localised organs into which the cancer is spread. The peritonectomy is done to remove the cancer, and is followed by chemotherapy aimed at eliminating residual disease. This major surgery will only be considered in cases involving patients who are fit, and where the disease has been diagnosed at an early stage. The surgery is not curative, and the purpose of the surgery is to relieve symptoms and prolong life.
As with pleural mesothelioma, chemotherapy is another major treatment option for peritoneal mesothelioma patients. Chemotherapy drugs are used to shrink tumours and slow down cancerous progress. The treatment can be used before, during or after surgery, and is also used when surgery is not proposed. Chemotherapy drugs which have been shown to have positive effects for peritoneal mesothelioma include penetraxed, cisplatin, carboplatin and gencitabin. Heated chemotherapy procedures are being used where the chemotherapy drugs are warmed and administered directly into the abdominal cavity. The treatment is often combined with cytoreductive surgery and works best for early stage patients.
Radiotherapy is not typically recommended to slow cancer growth in peritoneal mesothelioma. It is usually considered too risky with vital abdominal organs nearby.