2023 World Conference on Lung Cancer (Posters)-P2.21. The Significance of BAP1 and MTAP/CDKN2A Expression in Well-Differentiated Papillary Mesothelial TUmour: A Series of 21 Cases

P2.21. The Significance of BAP1 and MTAP/CDKN2A Expression in Well-Differentiated Papillary Mesothelial TUmour: A Series of 21 Cases - PDF(Abstract)

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This presentation discusses the significance of BAP1 and MTAP/CDKN2A expression in well-differentiated papillary mesothelial tumors (WDPMT). The 2021 WHO classification renamed WDPMT to avoid confusion with mesothelioma. WDPMT is characterized by papillae lined by mesothelial cells, but the BAP1/MTAP status is not defined. The new classification also introduces mesothelioma in situ (MIS), diagnosed by loss of MTAP/CDKN2A or BAP1. The significance of BAP1/MTAP loss in lesions resembling WDPMT has not been studied. <br /><br />Clinical and pathological data for 21 lesions diagnosable as WDPMT were retrieved from cases diagnosed between 2003-2023. BAP1 was assessed by immunohistochemistry, and MTAP/CDKN2A by FISH. The results showed that 43% of cases had loss of BAP1, and 21% had loss of MTAP/CDKN2A expression. Four of the cases with BAP1 loss progressed to mesothelioma after two to six years. None of the cases with MTAP/CDKN2A loss progressed to mesothelioma. Six patients had recorded exposure to asbestos, and three of them progressed to mesothelioma.<br /><br />The study concludes that asymptomatic lesions with intact BAP1 and MTAP have a low risk of progression. Cases with WDPMT morphology but loss of BAP1 should be classified as papillary MIS, as they have a risk of progression to mesothelioma. The significance of loss of MTAP is uncertain. <br /><br />Keywords for the presentation are mesothelioma, well-differentiated papillary mesothelioma, and BAP1. The presentation is part of the track on Mesothelioma, Thymoma, and Other Thoracic Tumors.

Asset Subtitle

Sarita Prabhakaran

Meta Tag

Speaker Sarita Prabhakaran

Topic Mesothelioma, Thymoma & Other Thoracic Tumors: Translational

Keywords

BAP1

MTAP/CDKN2A

well-differentiated papillary mesothelial tumors

WDPMT

2021 WHO classification

mesothelioma

mesothelioma in situ

MIS

immunohistochemistry

FISH