A case of slowly progressive malignant pericardial mesothelioma suggesting the involvement of BAP1 loss

Abstract

Malignant pericardial mesothelioma (MPM) is a rare tumour that arises from the mesothelial cells of the pericardium. No standard treatment has been established owing to a poor treatment response; therefore, MPM has a poor prognosis. We herein report a rare case of MPM in a 70-year-old man that was diagnosed immunohistopathologically using cell block sections of pericardial fluid and in which longterm survival for more than 3 years was achieved with only periodic pericardial drainage. Immunohistopathological staining investigations, especially BRCA1-associated protein 1 (BAP1) immunostaining using cell block sections of pericardial effusion, are effective in making a diagnosis of MPM. Well-differentiated papillary mesothelioma (WDPM) with BAP1 loss progresses to MPM in the long term, showing that BAP1 loss may induce phenotypical evolution of WDPM. BAP1 loss may also progress to malignant mesothelioma in situ and then to invasive mesothelioma. BAP1 immunohistochemistry should be considered for the early diagnosis of MPM.

Pericardial Mesotheliomas

“…BAP-1 alterations were found in 2 patients by next-generation sequencing and immunohistochemistry, respectively 9–11. Interestingly, Fukasawa et al10 reported a patient with PM with loss of BAP-1 by immunohistochemistry, who was alive after 3 years of follow-up, in concordance with the longer survival observed in pleural mesotheliomas with BAP-1 mutations. Two reports alluded to the evaluation of BAP-1 in PM, which is commonly lost in pleural mesotheliomas; of these, 2 cases had a deletion of BAP-1 , as demonstrated by fluorescence in situ hybridization (FISH) 12,13…”

“…Germline mutations of the BAP-1 gene are known to be present in a proportion of pleural mesotheliomas; however, BAP-1 testing has been reported in only four cases of PM. BAP-1 alterations were found in 2 patients by next-generation sequencing and immunohistochemistry, respectively 9–11. Interestingly, Fukasawa et al10 reported a patient with PM with loss of BAP-1 by immunohistochemistry, who was alive after 3 years of follow-up, in concordance with the longer survival observed in pleural mesotheliomas with BAP-1 mutations.…”

The clinical outcome, pathologic spectrum, and genomic landscape of 454 cases of salivary mucoepidermoid carcinoma

“…cell metabolism [37] , cellular differentiation [38,39] , and immune regulation [40,41] . Of the four tumors with BAP1 mutations in our study, two were substitutions and two were truncations.…”