BAP1 immunohistochemistry and p16 FISH results in combination provide higher confidence in malignant pleural mesothelioma diagnosis: ROC analysis of the two tests

Our plain-English summary of BAP1 immunohistochemistry and p16 FISH results in combination provide higher confidence in malignant pleural mesothelioma diagnosis: ROC analysis of the two tests, by T. Hida, M. Hamasaki, S. Matsumoto, et al (Pathology International, 2016).

The study

• Authors: T. Hida, M. Hamasaki, S. Matsumoto, A. Sato, T. Tsujimura, K. Kawahara, A. Iwasaki, T. Okamoto, Y. Oda, H. Honda, K. Nabeshima
• Journal: Pathology International
• Published: 2016;66(10):563-570
• Cited by: 65 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Differentiation of malignant pleural mesothelioma (MPM) from benign mesothelial proliferation remains problematic. Loss of nuclear staining of BRCA1-associated protein 1 (BAP1; detected using immunohistochemistry (IHC)) and homozygous deletion (HD) of p16 (detected using fluorescence in situ hybridization (FISH)) are useful for differentiation of MPM from reactive mesothelial hyperplasia (RMH), but the correlation between BAP1 expression loss and p16 HD has not been fully described. We performed BAP1 IHC and p16-specific FISH for 40 MPM and 20 RMH cases, and measured proportions of cells showing BAP1 expression and p16 HD for each case. The diagnostic accuracy for MPM and the cut-off values of the two methods were assessed using receiver operating characteristic (ROC) analysis. BAP1 expression loss, p16 HD and coexistence of both were present in 27 (67.5 %), 27 (67.5 %) and 17 (42.5 %) MPM cases, respectively. Three MPM cases (7.5 %) and all 20 RMH cases had neither BAP1 loss nor p16 HD. There was no correlation between the results of the two methods. Their combination showed higher sensitivity (92.5 %, 37/40) and estimated probability than BAP1 IHC and p16-specific FISH used alone. BAP1 IHC and p16-specific FISH have independent diagnostic value, and have increased reliability when used in combination, for MPM diagnosis.

© 2016 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.

In plain English

This study tested two laboratory methods for distinguishing malignant pleural mesothelioma from reactive mesothelial hyperplasia, a benign look-alike condition. The authors examined archived tissue from 40 mesothelioma and 20 hyperplasia cases (from patients with bullae) at Fukuoka University Hospital, Japan, 2001 to 2015. They used BAP1 staining (immunohistochemistry) and p16 deletion testing (FISH). Asbestos exposure was not studied. With cut-offs set by ROC analysis, loss of BAP1 nuclear staining and homozygous deletion of p16 were each found in 27 of 40 mesothelioma cases (67.5 %) and in none of the 20 hyperplasia cases. Seventeen cases had both findings, and 3 had neither. The two results were not significantly correlated. Combined, the tests identified 37 of 40 cases (92.5 %). The area under the curve was 0.95 (95 % CI 0.84 to 0.99), compared with 0.84 (0.71 to 0.91) for BAP1 and 0.74 (0.60 to 0.85) for p16. The authors concluded that the tests have independent diagnostic value and give more confidence when combined. They noted the small sample, the exclusion of sarcomatoid tumors, and that BAP1 gene changes were not tested in each case.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective diagnostic accuracy study of archived pathology cases using receiver operating characteristic (ROC) analysis, with supporting tests on mesothelioma cell lines
• Who was studied: 40 malignant pleural mesothelioma cases: 34 male and 6 female, mean age 63.0 years, 35 epithelioid and 5 biphasic, with sarcomatoid tumors excluded. 20 reactive mesothelial hyperplasia cases from patients with bullae: all male, mean age 34.5 years. All came from the pleural lesion files of Fukuoka University Hospital, Japan, 2001 to 2015. Five mesothelioma cell lines and one non-neoplastic mesothelial cell line were also tested.
• Exposure: Asbestos exposure was not examined. The study assessed two diagnostic tests: BAP1 immunohistochemistry and p16 FISH.
• Main results:
  • With a BAP1 cut-off of 19.7 %, loss of BAP1 nuclear staining was found in 27 of 40 mesothelioma cases (sensitivity 67.5 %). It was found in none of the 20 hyperplasia cases (specificity 100 %).
  • With a p16 cut-off of 11.0 %, p16 homozygous deletion was found in 27 of 40 mesothelioma cases (67.5 %). All 20 hyperplasia cases were negative.
  • 17 of 40 mesothelioma cases (42.5 %) had both BAP1 loss and p16 deletion. 3 cases (7.5 %) were negative on both tests.
  • The correlation between the BAP1 and p16 results was not statistically significant (Fisher's exact test P = 0.4814; Spearman's rho = 0.1457).
  • The area under the ROC curve was 0.84 (95 % CI 0.71 to 0.91) for BAP1 and 0.74 (95 % CI 0.60 to 0.85) for p16; this difference was not statistically significant (P = 0.3153). For the combined tests it was 0.95 (95 % CI 0.84 to 0.99), significantly higher than BAP1 alone (P = 0.0332) and p16 alone (P = 0.0005).
  • Combined, the tests detected 37 of 40 mesothelioma cases with 100 % specificity. Sensitivity was 92.5 % in the table and 93 % in the text.
  • Two mesothelioma cell lines with known BAP1 gene alterations showed no BAP1 staining (0.0 %). Three cell lines with wild-type BAP1 kept their staining.
  • BAP1 results did not differ significantly between the 16 mesothelioma cases given chemotherapy before surgery or biopsy and the other mesothelioma cases.
• The authors' conclusion: The authors concluded that BAP1 immunohistochemistry and p16 FISH each have independent diagnostic value for separating mesothelioma from reactive hyperplasia, and that combining them increased sensitivity and confidence in the diagnosis. They added that the mesothelial origin of a tumor should first be confirmed with standard markers.
• Limitations the authors state:
  • The number of cases was relatively small, and the authors called for a larger study.
  • Only epithelioid and biphasic mesotheliomas were included; sarcomatoid cases were excluded.
  • BAP1 gene alteration was not tested in each case, and loss of BAP1 staining may not always be due to a gene alteration.
  • The two tests could not be evaluated on the same cells.
  • Patchy BAP1 staining may cause discrepancies in reading results. Benign tissue may sometimes be wrongly read as BAP1-negative, especially in small biopsies.
  • BAP1 loss can occur in other malignant tumors, so mesothelial origin must be confirmed first.
  • Some mesotheliomas may not be detected even when both tests are combined; 3 cases were negative on both.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: BAP1, Immunohistochemistry, Fluorescence In Situ Hybridization (FISH), Pleural Mesothelioma, Homozygous Deletion, Reactive Mesothelial Hyperplasia.

Related studies

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• Utility of BAP1 Immunohistochemistry and p16 (CDKN2A) FISH in the Diagnosis of Malignant Mesothelioma in Effusion Cytology Specimens — H.C. Hwang, B.S. Sheffield, et al. (2016)
• A combination of MTAP and BAP1 immunohistochemistry in pleural effusion cytology for the diagnosis of mesothelioma — Y. Kinoshita, T. Hida, et al. (2018)
• Fluorescence in situ hybridization (FISH) provides estimates of minute and interstitial BAP1, CDKN2A, and NF2 gene deletions in peritoneal mesothelioma — S. Brich, F. Bozzi, et al. (2020)
• BAP1 immunohistochemistry and p16 FISH to separate benign from malignant mesothelial proliferations — B.S. Sheffield, H.C. Hwang, et al. (2015)
• Immunohistochemical detection of MTAP and BAP1 protein loss for mesothelioma diagnosis: Comparison with 9p21 FISH and BAP1 immunohistochemistry — T. Hida, M. Hamasaki, et al. (2017)

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