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Marie Christine Aubry



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    MA23 - Preclinical Models and Genetics of Malignant Pleural Mesothelioma (ID 353)

    • Event: WCLC 2019
    • Type: Mini Oral Session
    • Track: Mesothelioma
    • Presentations: 1
    • Now Available
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      MA23.07 - Loss of Expression of BAP1 and/or MTAP Aids in the Diagnosis of Malignant Mesothelioma Metastatic to Lymph Nodes (Now Available) (ID 1121)

      14:30 - 16:00  |  Author(s): Marie Christine Aubry

      • Abstract
      • Presentation
      • Slides

      Background

      Stage and histology are the strongest prognostic parameters in malignant pleural mesothelioma and aid management of patients. However, the distinction between reactive intranodal mesothelial cells and metastatic malignant mesothelioma (MM) can be challenging. Loss of BRCA1 associated protein-1 (BAP1) and/or methylthioadenosine phosphorylase (MTAP) expression has been identified in a subset of MM but not in reactive mesothelial proliferation. We investigated the value of these markers in the distinction between reactive mesothelial cells and metastatic MM in lymph nodes.

      Method

      Surgical files of Mayo Clinic Rochester (1996-2018) were searched for metastatic MM in lymph nodes. All cases and if available corresponding primary MM were reviewed by a thoracic pathologist (ACR) to confirm the diagnosis. Primary MM and lymph nodes were stained with BAP1 (clone C-4) and MTAP (2G4). Absence of nuclear staining of BAP1 and absence of nuclear and cytoplasmic staining of MTAP in essentially all tumor cells was considered as loss of expression.

      Result

      Forty-four patients (25 males, 56.8%) had a median age of 64 years (range, 24-75) at time of surgery. Tissue was available from nodal metastases in all cases, either paired with the primary MM at time of nodal sampling (N=37) or at a different time (N=4) (time between tissue collections, range, 1day- 4 years, respectively), or without paired primary MM (N=3). Thirty-seven pleural, 6 peritoneal and 1 pericardial MM were of epithelioid (N=39) or biphasic (N=5) subtype. Patients underwent extrapleural pneumonectomy (N=17), pleurectomy (N=7), resection (N=9), debulking (N=2), biopsy (N=8), or autopsy (N=1). In nodal metastases, BAP1 and/or MTAP expression was lost in 29 (of 43, 67.4%) cases; specifically, BAP1 expression was lost in 28 (of 44, 63.6%), MTAP was lost in 14 (of 43, 32.6%), and both were lost in 12 (of 43, 27.9%) cases. Agreement in expression/loss of expression of BAP1 and/or MTAP in primary and metastatic MM occurred in all cases. During a median follow up of patients who underwent extrapleural pneumonectomy or pleurectomy (available in N=23) of 14.8 months (range, 1-119) 17 patients died within a median time of 16 months.

      Conclusion

      BAP1 and MTAP immunostains are helpful in the distinction between metastatic MM and reactive mesothelial cells in lymph nodes when one or both markers lost expression in the mesothelial cells. Expression of both markers does not exclude the possibility of metastatic MM.

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