How Is Mesothelioma Diagnosed?
Mesothelioma can be diagnosed by the cytologic analysis of pleural fluid or by the histologic assessment of a tissue sample (obtained either by using a needle or with a surgical biopsy). However, in some cases neither the cytological analysis of the pleural fluid nor the evaluation of a needle biopsy specimen can provide a definite and accurate diagnosis. A high degree of suspicion for MPM and uncertainties regarding its exact subtype remain a major concern. In that case, in order to get an accurate and definitive diagnosis, it is advised to conduct the analysis of a large enough tumor sample that is obtained surgically. A comprehensive histologic diagnosis is based both on the appearance of the tissue under the microscope and on specific staining used to confirm the diagnosis of MPM and to exclude the existence of other types of malignancies that are prevalent in the chest cavity (for example, lung cancer and metastatic nodules originating from other solid cancers).
How is a new MPM patient evaluated?
The primary aim in evaluating a new MPM patient is to obtain a comprehensive understanding of the patient’s disease stage and of the patient’s general health condition with a particular emphasis on pulmonary and cardiac performance status. To obtain the most accurate diagnosis, MTC has a dedicated team of medical experts from numerous fields including radiologists, surgeons, oncologists, pathologists, and pulmonologists to carry out all phases of the process. Once a comprehensive assessment is achieved, a treatment plan will be specifically tailored to fit the patient’s disease characteristics, general health and wishes.
Physicians will use a combination of your medical records, history and physical exam (symptoms, etc.) as well as clinical and radiological testing. In many cases, they will also recommend performing some invasive tissue sampling in order to delineate the precise disease stage, which is critical in order to devise the best treatment plan.
There are several steps in the staging and evaluation process:
- History and Physical exam. We will review your medical history, including any history of asbestos exposure. We also perform a complete physical exam.
- Clinical tests. Simple clinical exams such as a six-minute walk test may provide important information about the function of your lungs.
- Pulmonary function test. This test estimates the volumes of air that you can inhale and exhale as well as the total volume of your lungs. This test can help diagnose lung diseases and measures their severity.
- Imaging. Several imaging studies may be performed to identify the presence of mesothelioma and determine if it has spread. Other imaging studies will help measure and quantify the function of your heart and lungs. The imaging studies include:
- Chest X-ray. A X-ray can show whether the pleura (the sac that covers the lungs and lines the chest wall) has thickened. It will also reveal any existing calcium deposits on the pleura. An X-ray also can show whether there is an accumulation of fluid around the lungs (called pleural effusion) or in the abdomen (often referred to as ascites).
- Computed Tomography (CT). A CT scan helps define the extent of the tumor. The CT scan is an X-ray procedure in which a scanner rotates around the body to produce detailed, cross-sectional images. A CT scan helps determine the location, size, and extent of mesothelioma tumors and can help determine whether the tumor has spread.
- Positron Emission Tomography Computed Tomography (PET-CT). A PET-CT scan will show your treatment team the extent of the tumor. It does this by using the fact that malignant cells take up sugar faster than normal cells. Thus the scan will show the location of tumor cells. This will help in your treatment planning.
- Magnetic Resonance Imaging (MRI). An MRI uses radio waves and strong magnets instead of X-rays. It produces cross sectional images of the body like a CT scanner, but it also can produce images that are parallel with the length of your body (both front to back and side to side), providing more detailed information to refine the staging and better delineate the extent of the disease.
- Echocardiogram. An echocardiogram uses ultra-high-frequency sound waves to create an image of the heart muscle. An “echo” test can provide useful information, including the size and shape of the heart, its pumping strength, and the location and extent of any damage or heart disease.
- Ventilation / Perfusion scan (VP). A VP scan is a nuclear medicine scan that uses radioactive material (radiopharmaceutical) to examine airflow (ventilation) and blood flow (perfusion) in the lungs. The aim of the scan is to determine the contribution of each of your lungs to your breathing effort.
- Surgical Staging. Three surgical sights may be explored as part of the staging of MPM. These are the thorax (chest); the anterior mediastinum (the space just anterior to the main airway; and the peritoneum (abdominal cavity). These spaces are explored using minimally invasive surgical techniques.
- The chest (thorax) may be explored by a procedure called video-assisted thoracoscopy. It will require one or two small incisions in the chest, which are used to insert a small video camera and instruments. This procedure is done only in case the surgeon feels that further data regarding the extent of disease in the thorax is required or in cases when additional tumor tissue is required to confirm the diagnosis.
- The mediastinum may be explored by a procedure called a mediastinoscopy. It will require one small incision at the base of the neck, which is used to insert a small video camera and instruments. This procedure facilitates the sampling of lymph nodes in the mediastinum and provide valuable data regarding the spread of disease to this site. Positive involvement of lymph nodes in the mediastinum may guide chemotherapy. A negative finding may permit surgery.
- The peritoneum may be explored by a procedure called a laparoscopy. It will require a few small incisions in the abdomen, which are used to insert a small video camera and instruments. This procedure allows the surgeon to assess the abdominal cavity for invasion by MPM, the undersurface of the diaphragm is inspected as well as the entire abdomen. Further, the abdominal cavity is washed and the products are sent for cytological analysis. In addition, random peritoneal biopsies may be collected. Positive involvement of the peritoneal cavity may guide chemotherapy. A negative finding may indicate a surgical option.
Factors affecting MPM Outcomes and Mesothelioma Survival Rates
Disease stage is a very important prognostic marker. It is determined by defining the local disease load (tumor denominator) as well as its spread to lymphatic organs (nodal denominator) and to distant sites (metastasis). Early disease stage is associated with improved outcomes and it is a critical variable affecting the design of the treatment plan. Therefore, at MTC, we perform a rigorous staging procedure to determine as accurately as possible the disease stage prior to recommending a definite treatment plan. This further provides us with the data needed to more accuracy predict the patient’s prognosis and potential to benefit from surgery.
The MPM histological subtype also greatly affects survival, with the epithelioid subtype having the best prognosis and the sarcomatoid subtype having the worst. Other factors that may predict a favorable outcome include younger age, female gender, good performance status (determined during initial testing), early-stage disease, and lack of chest pain at diagnosis.