In an article in the journal Pathology, the team claims that a definitive diagnosis of mesothelioma can be made from a sample of excess lung fluid. Excess fluid collection around the lungs, called pleural effusion, is common in people with mesothelioma and several other kinds of cancer. Approximately 70 percent of people with mesothelioma develop pleural effusions. Because effusion is often one of the earliest signs of the disease, the Japanese doctors maintain that this fluid could be useful for making an early mesothelioma diagnosis.
“Early in the incidence of mesothelioma, there is just effusion, without pleural thickening, and in some cases mesothelioma cells appear in effusions temporarily, not permanently,” writes lead study author Toshiaki Kawai of the National Defense Medical College. “Therefore, correct diagnosis requires effusion-sampling at the right time.”
According to the researchers, accurate diagnosis of mesothelioma also depends on knowing what to look for under the microscope. Dr. Kawai and his colleagues say mesothelioma cells in pleural effusion form ball-like cell clusters, have multiple round or oval nuclei in a single cell, show a blurring of the cell contours, and have thick cytoplasm. When these cellular characteristics are present in people with a history of asbestos exposure and pleural thickening, the researchers say, “mesothelioma may be possible by effusion cytology alone”.
Because the symptoms of mesothelioma, such as cough and chest pain, can be vague and can mimic other conditions, mesothelioma is often a diagnostic challenge. Based on the patient’s history with asbestos, an imaging study such as PET-CT may be performed. If it reveals the characteristic thickening of the pleural lining and blood tests show certain mesothelioma biomarkers, a tissue sample may be taken to confirm the diagnosis.
An estimated 2,500 people undergo this process in the U.S. each year. Scientists around the globe continue to work on ways to simplify mesothelioma diagnosis for faster, earlier disease confirmation.
Kawai, T et al, “Pulmonary Pathology: SY22-2 Diagnosis of mesothelioma by cytology using Japanese criteria”, October 2014, Pathology, Epub ahead of print