Mesothelioma Diagnosis Challenges
Why is Mesothelioma so Difficult to Diagnose?
There are several reasons why patients who present with mesothelioma are often misdiagnosed. One of the biggest ones is that mesothelioma is an “orphan disease,” meaning it only affects a small percentage of the general population. According to the Mesothelioma Applied Research Foundation, “the numbers of newly affected individuals in the United States have been reported to be between 2,500 and 3,000 every year”. As a result, doctors aren’t as familiar with the disease as they are with other conditions like diabetes, breast cancer or heart disease.
Symptoms of the disease, such as chest pain, difficulty breathing and sudden weight loss, are another reason why it is so difficult to diagnose. According to Dr. Lee Krug, a thoracic oncologist at Memorial Sloan-Kettering Cancer Center, Director of the Mesothelioma Program at that institution, and a member of the National Comprehensive Cancer Network (NCCN) Guidelines Panel, “Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. In addition, a physician’s initial evaluation of a patient may reveal pleural effusion (accumulation of fluid between the layers of tissue that line the lungs and chest cavity), but it can often be missed on pleural fluid cytology (examination of the cells of the fluid under a microscope).” His comments appeared in a NCCN press release dated March 13, 2010.
However, Dr. Kruger went on to add that mesothelioma patients have elevated levels of Soluble Mesothelin-Relation Protein (SMRP) and another protein called Osteopontin, and these biomarkers may become significant in diagnosing the disease in earlier stages.
In many cases, diagnosis is further complicated by the fact that the pathologist has only a very small amount of biopsied tissue available for histological evaluation. This type of assessment uses a microscope evaluation of the tissue to determine if it is cancerous. If it is, then tests are performed to determine the type of cancer it is.
This problem is being compensated for through the recent use of video-assisted thoracoscopy (VAT) biopsies. This is a relatively new type of surgery that allows the doctor to see inside the chest cavity with only very small incisions. It also makes it possible to remove a mass that is close to the outer edges of the lung without the type of invasive surgery that was performed in the past. VAT has significantly increased the size of pleural biopsies and the choice of sampling sites, resulting in enough of the right kind of tissue to make an accurate diagnosis.
The appearance of malignant mesothelioma cells can vary greatly within the same patient when examined under the microscope. In addition, a number of other tumors, either beginning within the thorax, or spreading from sites outside the thorax can mimic malignant mesothelioma. There are also a number of non-cancerous conditions that affect the pleura or liquid-filled sac between the lungs and chest wall that are similar in appearance to pleural malignancy.
However, the recent widespread use of immunohistochemistry has substantially improved the accuracy of diagnosis. This is a complex pathological test that stains cancer cells with fluorescent dyes or enzymes in order to reveal specific proteins that are biomarkers for these types of cells.