Experience of the United States-Canadian Mesothelioma Reference Panel 1985-2026: Historical Review and New...

The United States-Canadian Mesothelioma Reference Panel was established in 1985. Data on the first 200 cases were published in 1991.

To review what has changed in mesothelial pathology since the first Mesothelioma Panel article was published.

Cases referred to the United States-Canadian Mesothelioma Reference Panel and published literature.

Panel accessions have reached 4000. The major problems for which the first 200 cases were referred were mesothelioma versus another tumor and mesothelioma versus a benign mesothelial proliferation, and these remain the most common issues that the panel adjudicates. In the 1990s the panel depended on histochemistry and a very limited set of immunohistochemical carcinoma markers, as well as electron microscopy, to separate mesotheliomas from other tumors; currently there is an overabundance of immunohistochemical markers for this purpose, only a few of which are really specific. In the 1990s the panel depended almost entirely on morphology to separate benign from malignant mesothelial processes, but the advent of genetic analysis has led to very reliable surrogate immunohistochemical and fluorescence in situ hybridization tests for this separation. New issues and entities that the panel briefly touched on (well-differentiated papillary mesothelial tumor) or did not deal with in the 1990s, including mesothelioma genetics, cytologic diagnosis of mesothelioma, mesothelioma in situ, and solid papillary mesothelial tumor, have been addressed by panel members and are reviewed here. Mesothelioma diagnostic pathology has undergone remarkable development during the past 40 years, such that most mesotheliomas can be readily diagnosed and separated from various mimics.