Fluorescence in situ hybridization in the definitive diagnosis of malignant mesothelioma in effusion cytology

Our plain-English summary of Fluorescence in situ hybridization in the definitive diagnosis of malignant mesothelioma in effusion cytology, by S. Savic, N. Franco, B. Grilli, et al (Chest, 2010).

The study

• Authors: S. Savic, N. Franco, B. Grilli, V. Barascud Ade, M. Herzog, B. Bode, H. Loosli, P. Spieler, R. Schönegg, I. Zlobec, D.P. Clark, J.G. Herman, L. Bubendorf
• Journal: Chest
• Published: 2010;138(1):137-44
• Cited by: 64 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Distinction of malignant mesothelioma (MM) from reactive mesothelial cells (RM) in effusions is notoriously difficult. The aim of our study was to test chromosomal aberrations detected by fluorescence in situ hybridization (FISH) in the diagnosis of MM in effusion cytology and to explore the potential role of p16, p14, and p15 gene methylation as an alternative mechanism of tumor suppressor gene inactivation.

Methods: Fifty-two effusions of biopsy-proven MM and 28 benign effusions were retrospectively analyzed by multitarget FISH assay for aberrations of chromosomes 3, 7, 17, and 9p21. In case of a negative result, the corresponding MM biopsy specimen was analyzed. Methylation-specific polymerase chain reaction (MSP) for p16, p14, and p15 was performed on FISH-negative MM biopsy specimens.

Results: Seventy-nine percent of effusions with biopsy-proven MM had chromosomal aberrations, with loss of 9p21 as the most common finding. All benign effusions were FISH negative. Sensitivity, specificity, and positive and negative predictive values for detection of MM by FISH were 79%, 100%, 100%, and 72%, respectively. Six of nine FISH-negative effusions with biopsy-proven MM were also FISH negative in the MM biopsy specimens. Four of five FISH-negative biopsy specimens showed promoter methylation in p16 and p14 as compared with one of 12 benign controls.

Conclusions: FISH is a sensitive and highly specific method for the definitive diagnosis of MM in effusion cytology. In the subset of FISH-negative MM, tumor suppressor genes on the chromosomal region 9p21 are often inactivated by promoter methylation.

In plain English

This retrospective Swiss study tested whether multitarget fluorescence in situ hybridization (FISH), a laboratory test, could distinguish malignant mesothelioma from benign (reactive) mesothelial cells in body-fluid samples. The test looks for extra copies of chromosomes 3, 7 and 17 and loss of the 9p21 region. The authors analyzed archived effusions from 2003 to 2007: 52 from patients with biopsy-proven mesothelioma (48 pleural, four ascites) and 28 benign pleural effusions. The study did not examine asbestos exposure. FISH found chromosomal abnormalities in 41 of 52 mesothelioma effusions (79%) and none of the 28 benign effusions: sensitivity 78.8% (95% confidence interval 73.5% to 78.8%), specificity 100% (95% confidence interval 90.1% to 100%). Loss of 9p21 was the most common change. FISH was also positive in 22 of 23 effusions from metastatic adenocarcinoma, so the authors stressed first confirming that the cells are mesothelial. Four of five FISH-negative mesothelioma biopsies showed methylation (chemical silencing) of the p16 and p14 genes. The authors concluded that FISH is a valuable addition to effusion cytology and that their findings need confirming in a larger, independent cohort.

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 effusion cytology specimens, using multitarget FISH (UroVysion assay), with methylation-specific PCR on selected biopsy specimens
• Who was studied: A consecutive series of 52 patients with biopsy-proven malignant mesothelioma (48 pleural effusions, 4 ascites) from four Swiss pathology institutes (Basel, Bern, Zurich, St. Gallen) and 28 patients with benign pleural effusions from Basel, March 2003 to December 2007. A further 23 effusions from metastatic adenocarcinomas served as a comparison group.
• Exposure: No asbestos or other exposure was studied. The article evaluated a laboratory diagnostic test (FISH for chromosomes 3, 7, 17 and 9p21) and gene methylation of p16, p14 and p15.
• Main results:
  • Chromosomal aberrations were found by FISH in 41 of 52 effusions (79%) from patients with biopsy-proven mesothelioma.
  • All 28 benign pleural effusions with reactive mesothelial cells were FISH negative.
  • FISH had a sensitivity of 78.8% (95% CI, 73.5%-78.8%) and a specificity of 100% (95% CI, 90.1%-100%) for mesothelioma.
  • The positive predictive value was 100% (95% CI, 93.2%-100%) and the negative predictive value was 71.8% (95% CI, 64.7%-71.8%).
  • 9p21 deletion was present in 38 of 40 evaluable FISH-positive mesothelioma effusions (95%).
  • Of nine FISH-negative mesothelioma effusions with an evaluable matched biopsy, six were also FISH negative in the biopsy. The other three biopsies were FISH positive, which the authors attributed to sampling error in the effusions.
  • FISH was positive in 22 of 23 effusions (96%) from metastatic adenocarcinomas.
  • Four of five FISH-negative mesothelioma biopsy specimens showed promoter methylation of p16 and p14. Only one reactive pleural effusion had methylation of both genes.
  • p16 methylation was significantly associated with mesothelioma: 8 of 17 mesothelioma specimens (47%) versus 1 of 13 reactive effusions (8%), P = .042. p15 methylation was significantly associated with reactive effusions: 10 of 13 reactive effusions (77%) versus 5 of 16 mesothelioma specimens (31%), P = .025.
  • Simultaneous p16 and p14 methylation was significantly more frequent in FISH-negative mesothelioma than in mesothelioma with 9p21 deletion and in negative controls (P less than .01 each).
• The authors' conclusion: The authors concluded that multitarget FISH is a valuable adjunct to conventional effusion cytology that might allow a definitive diagnosis of mesothelioma. They also concluded that in the small subset of FISH-negative mesothelioma, tumor suppressor genes at 9p21 are often inactivated by promoter methylation, and that these findings should be confirmed in a large, independent cohort.
• Limitations the authors state:
  • Chromosomal aberrations are not specific for mesothelioma: metastatic carcinomas are also FISH positive, so the mesothelial origin of the cells must be established first.
  • Negative FISH results in some effusions were attributed to sampling error, because the effusions may have contained few or no tumor cells.
  • The methylation findings come from a small number of FISH-negative cases and need study in more patients. Promoter methylation is not exclusive to malignant tumors: p15 methylation was found in normal lymphocytes.
  • The authors stated that the findings should be confirmed in a large, independent cohort.

Topics

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

Medical terms in this study, explained in our Lexicon: Fluorescence In Situ Hybridization (FISH), Malignant Mesothelioma, Cytology, Reactive Mesothelial Cells, Tumor Suppressor Gene, Biopsy.

Related studies

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• 9p21 deletion in the diagnosis of malignant mesothelioma, using fluorescence in situ hybridization analysis — M. Takeda, T. Kasai, et al. (2010)
• Common Fluorescence In Situ Hybridization Applications in Cytology — S. Savic, L. Bubendorf (2016)
• Adaptation of a commercial fluorescent in situ hybridization test to the diagnosis of malignant cells in effusions — C. Flores-Staino, E. Darai-Ramqvist, et al. (2010)
• Hemizygous loss of NF2 detected by fluorescence in situ hybridization is useful for the diagnosis of malignant pleural mesothelioma — Y. Kinoshita, M. Hamasaki, et al. (2020)
• 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)

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