Mesothelioma is an aggressive malignancy primarily associated with exposure to asbestos dust. It’s most common site is on the pleura, the membrane that surrounds the lungs. The second most common site for mesothelioma tumors – accounting for about 30% of cases – is the peritoneal membrane that lines the abdomen.
A number of studies in recent years have suggested that, like many other types of cancer, mesothelioma also has a genetic component and people with certain kinds of abnormalities may be more prone to develop it. Now, a new study conducted by Japanese pathologists has also uncovered genomic differences between people with the peritoneal or pleural types of the disease.
Using a chromosome test called FISH (fluorescence in situ hybridization), the team analyzed tissue samples of 54 cases of mesothelioma, including 40 pleural cases and 14 peritoneal. They found that 85% (34 out of the 40) of pleural cases showed deletion of the 9p21 chromosome, a gene that has been linked to cardiovascular disease. Only 36% of the peritoneal mesothelioma tissue samples showed the same deletion.
In contrast, the 14 peritoneal mesothelioma samples showed amplification in two other chromosomes – 5p15 and 7p12. Tissue samples from people with pleural mesothelioma did not show this amplification. None of the other genes studied appeared to influence the site of the mesothelioma.
“Our study suggests that the pathway of the genetic abnormality might vary between pleural and peritoneal malignant mesothelioma,” writes lead author Dr. Maiko Takeda from the Department of Diagnostic Pathology at Nara Medical University in Japan.
Evidence of 9p21 deletion has been used as a way to distinguish between malignant mesothelioma and a benign condition called reactive mesothelial proliferation (also called reactive mesothelioma hyperplasia). But Dr. Takeda and his colleagues say their findings highlight the fact that lack of 9p21 deletion does not necessarily rule out the possibility of mesothelioma, especially on the peritoneum.
The multi-center study was published in a recent issue of the Journal of Clinical Pathology.
Takeda, M et al, “Comparison of genomic abnormality in malignant mesothelioma by the site of origin”, September 12, 2014, Journal of Clinical Pathology, Epub ahead of print