BACKGROUND: The important diagnostic challenge facing the cytopathologist is whether a mesothelial proliferation on effusions represents a malignant mesothelioma (MM) or a benign mesothelial hyperplasia (MH). Here, we evaluated the diagnostic utility of BAP1 immunohistochemistry (IHC) in distinguishing between reactive and neoplastic mesothelial cells. METHODS: In pleural and peritoneal effusions from 147 patients with diagnosed MM or with a differential diagnosis of MM and MH, the expression of BAP1 was examined by IHC on paraffin-embedded cell blocks (n = 121) and biopsies (n = 44). Included were also synchronous and methacronous cytology/biopsy pair samples. BAP1 IHC was evaluated for nuclear staining as positive or negative on target mesothelial cells, with appropriate internal control. RESULTS: In MM cases, loss of BAP1 nuclear staining was observed in 76.5% of the cell blocks and 47.5% of the biopsies. All BAP1-negative cases with a differential diagnosis of benign and malignant mesothelial proliferations were MM at follow-up. All MH cases, the 29% of epithelial MM and the 90% of nonepithelial MM, retained BAP1 expression. Synchronous and methacronous biopsy/cytology pairs showed matching BAP1 results. CONCLUSION: In effusions with mesotheliomatous cells or atypical mesothelial cells of uncertain significance, negative BAP1 IHC strongly supports a diagnosis of MM. With prudence in interpreting immunostaining, BAP1 may be included in IHC panels for MM cytodiagnosis, given its high specificity and sensitivity.
BACKGROUND: The important diagnostic challenge facing the cytopathologist is whether a mesothelial proliferation on effusions represents a malignant mesothelioma (MM) or a benign mesothelial hyperplasia (MH). Here, we evaluated the diagnostic utility of BAP1 immunohistochemistry (IHC) in distinguishing between reactive and neoplastic mesothelial cells. METHODS: In pleural and peritoneal effusions from 147 patients with diagnosed MM or with a differential diagnosis of MM and MH, the expression of BAP1 was examined by IHC on paraffin-embedded cell blocks (n = 121) and biopsies (n = 44). Included were also synchronous and methacronous cytology/biopsy pair samples. BAP1 IHC was evaluated for nuclear staining as positive or negative on target mesothelial cells, with appropriate internal control. RESULTS: In MM cases, loss of BAP1 nuclear staining was observed in 76.5% of the cell blocks and 47.5% of the biopsies. All BAP1-negative cases with a differential diagnosis of benign and malignant mesothelial proliferations were MM at follow-up. All MH cases, the 29% of epithelial MM and the 90% of nonepithelial MM, retained BAP1 expression. Synchronous and methacronous biopsy/cytology pairs showed matching BAP1 results. CONCLUSION: In effusions with mesotheliomatous cells or atypical mesothelial cells of uncertain significance, negative BAP1 IHC strongly supports a diagnosis of MM. With prudence in interpreting immunostaining, BAP1 may be included in IHC panels for MM cytodiagnosis, given its high specificity and sensitivity.
Authors: Meredith Stevers; Joseph T Rabban; Karuna Garg; Jessica Van Ziffle; Courtney Onodera; James P Grenert; Iwei Yeh; Boris C Bastian; Charles Zaloudek; David A Solomon Journal: Mod Pathol Date: 2018-08-31 Impact factor: 7.842
Authors: Lucian R Chirieac; Yin P Hung; Assunta De Rienzo; David T Severson; Samuel Freyaldenhoven; Corinne E Gustafson; Nhien T Dao; Claire V Meyerovitz; Michela E Oster; Roderick V Jensen; Beow Y Yeap; Raphael Bueno; William G Richards Journal: J Pathol Date: 2020-10-15 Impact factor: 7.996