Clinical significance of 9P21 gene combined with BAP1 and MTAP protein expression in diagnosis and prognosis of mesothelioma serous effusion

The diagnostic value of the 9P21 gene determined using fluorescence in situ hybridization (FISH) combined with BRCA1-associated protein 1 (BAP1) and methylthioadenosine phosphorylase (MTAP) expression detection by immunohistochemistry, was investigated in serous effusion samples of malignant mesothelioma. A total of 70 serous disease samples with serous effusion were collected from June 2017 to June 2020. Following biopsy specimen pathological diagnosis, samples were divided into malignant mesothelioma and benign mesothelioma. Differential expression of BAP1 and MTAP genes were identified in mesothelioma and mesenchymal hyperplasia. The 9P21 gene fragment was lost in mesothelioma. The positive rates of FISH, BAP1 and MTAP in biopsy specimens were 98.00, 94.00 and 90.00%. The specificity of the three were 96.00, 85.71 and 77.27%, the sensitivity were 90.00, 95.92 and 93.75%, and the positive rate of the combined detection of the three was 93.33%. The positive rate of serous fluid samples detected by the three methods (9P21 FISH probe combined with BAP1 and MTAP expression detected immunohistochemically) was 96.00, 92.00 and 88.00%, the specificity were 90.00, 77.27 and 71.43%, the sensitivity was 96.00, 93.75 and 89.80%, and the positive rate of the three combined detections was 91.33%. It was demonstrated that there was a high consistency between serous fluid samples and biopsy samples. According to clinicopathological analysis, sex, age, lesion site, Ki67 had little association with the occurrence and development of malignant mesothelioma, while asbestos exposure history was closely associated to the occurrence of mesothelioma. A high level of BAP1 gene was positively associated with the prognosis of mesothelioma, while a high level of MTAP gene was negatively associated with the prognosis of mesothelioma (P<0.05). Therefore, 9P21 FISH probe combined with BAP1 and MTAP can be used as a new method for the detection of malignant mesothelioma, and provide an important basis for the early diagnosis of mesothelioma.