While the BAP1-mutated subgroup is similar to diffuse malignant pleural mesotheliomas, the TRAF7-mutated subgroup overlaps genetically with adenomatoid tumors and well-differentiated papillary mesotheliomas, in which recurrent TRAF7 mutations have been described.
Loss of BAP1 has recently been described as a highly specific marker for distinguishing malignant mesotheliomas (MM) from benign mesothelial proliferations (BMP).
The clinical phenotype of BAP1 hereditary cancer predisposition syndrome (MIM 614327) includes uveal melanoma (UM), cutaneous melanoma (CM), renal cell carcinoma (RCC), and mesothelioma.
A small number of mesotheliomas (probably in the order of 1%) are caused by germline mutations/deletions of BRCA1-associated protein-1 ( BAP1) in kindreds that also develop a variety of other cancers.
Moreover, many tumors harboring BAP1 germline mutations were associated with BAP1 syndrome, including mesothelioma and ocular/cutaneous melanomas, as well as renal, breast, lung, gastric, and basal cell carcinomas.
To identify additional driver genes, we used an integrated genomic analysis of 53 MPM tumor samples to guide a focused sequencing effort that uncovered somatic inactivating mutations in BAP1 in 23% of MPMs.
The discovery of inactivating mutations in the BRCA1-associated protein 1 gene in sporadic and hereditary mesothelioma has opened up a variety of novel molecular, clinical, and diagnostic investigations.
We conclude that: (1) BAP1 immunohistochemistry is relatively insensitive in the context of sarcomatous and desmoplastic mesotheliomas, but as a matter of time and cost efficiency may nonetheless be a useful first approach to the problem; (2) deletion of p16 by FISH is considerably more sensitive, but there remain a proportion of cases in which p16 is not deleted; (3) a small improvement in sensitivity can be achieved by using both markers; (4) in the context of a spindle cell malignant tumor in the pleura or peritoneum, which morphologically might be a metastatic sarcomatoid carcinoma or a mesothelioma, the finding of BAP1 loss favors mesothelioma, but p16 FISH cannot be used to separate sarcomatous mesotheliomas from sarcomatoid carcinomas.
UM is associated with an increased risk of cutaneous melanoma (CM) in addition to mesothelioma, skin lesions such as epithelioid atypical Spitz tumors, and other internal malignancies due to a germline mutation of the BRCA1-associated protein 1 (BAP1) gene.
Remarkable findings included the discovery of germline and somatic mutations of BRCA1 associated protein-1 (BAP1) in patients, and the genome-wide characterization of pathways altered in mesothelioma that could be potentially exploited to design novel therapeutic approaches.
BAP1 loss was detected in 61/88 (69%) tissues and in 20/30 (67%) cytology samples from mesothelioma with a specificity of 100% for both sampling methods.
To identify additional driver genes, we used an integrated genomic analysis of 53 MPM tumor samples to guide a focused sequencing effort that uncovered somatic inactivating mutations in BAP1 in 23% of MPMs.