While there are multiple methods for differentiating between benign and malignant mesothelioma cells, immunostaining the CD146 protein doesn’t appear to be one of them.
That’s the conclusion of a group of Canadian researchers after examining slides of CD146 stained with antibodies. The group’s findings appeared March 15 in the online edition of Virchows Archiv, a European pathology journal.
Prior research has suggested that stained CD146 proteins examined under a microscope can distinguish benign mesothelioma cells from malignant ones, though “there are marked differences in the reported results,” the research team noted.
To more conclusively decide on the technique’s effectiveness, the pathologists studied 123 slides of various types of mesothelioma cells. Thirty-two epithelioid reactive mesothelial hyperplasia samples were studied, along with samples for 43 epithelioid mesotheliomas, 17 spindle cell reactive mesothelial proliferations and 31 sarcomatoid mesotheliomas.
The team — composed of researchers from Vancouver General Hospital’s pathology department and the University of British Colombia’s pathology department — quickly hit a roadblock, as tests repeatedly yielded an array of false positives and sometimes uninterpretable results.
For example, when comparing epithelioid mesotheliomas to reactive epithelial mesothelial proliferations, the team found that staining produced very specific results — yielding 94 percent accuracy — but with dismal sensitivity — 23 percent — leading to many false-positive results, the study showed. Additionally, the intensity and extent of the staining also fared poorly in the tests.
When comparing sarcomatoid mesotheliomas to reactive spindle cell mesothelial processes, the team concluded that the tests were inadequate both in terms of sensitivity — 33 percent — and sensitivity, which they pegged at 76 percent.
Strong staining for slides of endothelial cells and fibroblasts fared much worse, with the team declining to even list their measurements, given how difficult they were to interpret.
By way of comparison, BAP1 gene samples were lost in 49 percent of epithelioid cell tests and only 29 percent of sarcomatoid mesothelioma slides, the researchers noted. The body’s MTAP enzyme was lost to only 23 percent of epithelioid tests and 24 percent of sarcomatoid mesothelioma tests. The researchers added that there was “no association between CD146 staining and BAP1 or MTAP retention/loss.”
Based on the overall results, the group concluded that “CD146 staining is probably not useful for separating malignant from benign mesothelial proliferations.”