Conclusions
Concordant BAP1, MTAP, and p16 expression is found between cytological and corresponding histological samples, indicating that a reliable diagnosis of MPM can be made on cytology only. Of the three markers, BAP1 and MTAP are most reliable in distinguishing malignant from reactive mesothelial proliferations.
Methods
Immunohistochemistry of BAP1, MTAP, and p16 was performed on cytological samples and compared with the corresponding histological specimen of 25 patients with MPM. Inflammatory and stromal cells served as positive internal control for all three markers. In addition, samples of 11 patients with reactive mesothelial proliferations served as an external control group.
Results
Loss of BAP1, MTAP, and p16 expression was found in 68%, 72%, and 92% of MPM, respectively. Loss of MTAP was associated with loss of p16 expression in all cases. Concordance of BAP1 between cytological and corresponding histological samples was 100% (kappa coefficient 1; p = 0.008). For MTAP and p16, kappa coefficient was 0.9 (p = 0.01) and 0.8 (p = 0.7788), respectively. Conclusions: Concordant BAP1, MTAP, and p16 expression is found between cytological and corresponding histological samples, indicating that a reliable diagnosis of MPM can be made on cytology only. Of the three markers, BAP1 and MTAP are most reliable in distinguishing malignant from reactive mesothelial proliferations.