The role and importance of BAP1, MTAP and 5-HMC immunohistochemical markers in diagnosis and prognosis in pleural malignant mesothelioma

The Role and Importance of BAP1, MTAP and 5-HMC Immunohistochemical Markers in Diagnosis and Prognosis in Pleural Malignant Mesothelioma Purpose: Mesotheliomas are the most common primary pleural tumors. One of the most important differential diagnoses of these tumors, which are rare and have a very poor prognosis, is benign lesions such as reactive mesothelial proliferations and fibrous pleuritis. Surrounding tissue invasion is a definite finding in favor of mesothelioma, however, it is not always possible to detect this feature in small biopsy materials. Since various immunohistochemical markers previously used for this purpose are not reliable enough, new markers are being investigated. The aim of this study is to investigate the role and importance of the current markers BAP1, MTAP and 5-hmC, in the diagnosis and prognosis of mesothelioma. Materials and Methods: 65 mesothelioma and 28 reactive mesothelial cell hyperplasia/chronic pleuritis/fibrous pleuritis cases diagnosed in Çukurova University Faculty of Medicine, Department of Medical Pathology between 2010-2017 were included in the study. BAP1, MTAP and 5-hmC antibodies were immunohistochemically applied to the formalin-fixed paraffin embedded block of the cases, and the loss of markers was evaluated. In the study, the effects of these markers on survival in mesothelioma cases were also examined. Results: BAP1, MTAP and 5-hmC are 100% specific in distinguishing pleural mesotheliomas from the benign group; the sensitivity of the markers was determined as 67.7%, 61.5% and 52.3%, respectively. When all three markers are used together, the sensitivity reached 95.4%. BAP1, MTAP and 5-hmC were not found to be statistically significantly associated with survival in all or subtypes of mesothelioma. Conclusion: Most mesothelioma cases do not meet the appropriate conditions for surgical resection at the time of admission to the hospital. For this reason, histopathological diagnosis of the cases is tried to be given with small biopsy samples. It is very difficult to make the differential diagnosis of reactive lesion and mesothelioma, especially in samples where the surrounding adipose tissue cannot be observed. In this distinction, current immunohistochemical markers BAP1, MTAP and 5-hmC are highly specific for mesothelioma. The combined use of these markers has higher sensitivity than their individual use. Therefore, the algorithmic application of these markers to use BAP1 in the first line in a lesion with proven mesothelial origin will enable the diagnosis of the majority of mesothelioma cases. Keywords: Pleura, mesothelioma, BAP1, 5-hmC, MTAP