Brca1-Associated Protein 1 (BAP1) Immunohistochemical Expression as a Diagnostic Tool in Malignant Pleural Mesothelioma Classification: a Large Retrospective Study

Malignant pleural mesothelioma (MPM) is a highly aggressive disease with limited therapeutic options. Histology remains among the most reliable prognostic factors, since epithelioid is associated with the best and sarcomatoid subtype with the worst prognosis. Biphasic subtype has an intermediate prognosis, but its definitive histological diagnosis may be challenging due to the difficult assessment of the neoplastic nature of the stromal component. Recent data identified BRCA1-Associated Protein 1 (BAP1) as one of the most frequently mutated genes in MPM. Immunohistochemistry for BAP1 has been proposed to be predictive for the detection of BAP1 mutation in neoplastic cells. The aim of the present study was to define the diagnostic usefulness of BAP1 immunohistochemical determination in MPM, with clinical-pathological correlation.