Adaptation of a commercial fluorescent in situ hybridization test to the diagnosis of malignant cells in effusions

Our plain-English summary of Adaptation of a commercial fluorescent in situ hybridization test to the diagnosis of malignant cells in effusions, by C. Flores-Staino, E. Darai-Ramqvist, K. Dobra, et al (Lung Cancer, 2010).

The study

• Authors: C. Flores-Staino, E. Darai-Ramqvist, K. Dobra, A. Hjerpe
• Journal: Lung Cancer
• Published: 2010;68(1):39-43
• Cited by: 42 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In effusion cytology, adjuvant techniques are often needed for the differentiation of reactive proliferating mesothelial cells and malignant cells. In the case of malignancy the further challenge is to distinguish metastatic tumors from the primary malignant mesothelioma. Fluorescence in situ hybridization (FISH) of cells in interphase is an accurate method to monitor the genetic status of cells, detecting aneuploid signals and gene deletions. Moreover, it has been proposed that a homozygous deletion of the p16(INK4A) gene could more specifically identify malignant mesothelial cells among the exfoliated cells. The first objective of this study was to adapt the commercial FISH-test, UroVysion originally designed for the cytological diagnosis of bladder cancer, to the analysis of cells in effusions. The second objective was to test the clinical utility of the test. Sixty-eight pleural effusions were evaluated. The cytological diagnosis was malignant in 29 cases, inconclusive in 24 cases and benign in 15 cases. The independently verified final diagnoses were mesothelioma in 21 cases, metastatic cancer in 29 and benign in 18 cases. The algorithm for aneuploidy distinguished almost all tested malignant conditions from benign ones, also those with inconclusive cytology. The 9p21 locus, carrying the p16(INK4A) gene, was homozygously deleted in two of the metastatic cancers, while this was seen in 12 of the 21 malignant mesotheliomas. Thus the commercial UroVysion-test can be used to accurately distinguish malignant and reactive cells in effusions, particularly when cytology is inconclusive. The test may also indicate presence of MM.

Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.

In plain English

This Swedish study adapted UroVysion, a commercial fluorescence in situ hybridization (FISH) test made for bladder cancer, to pleural effusions (fluid around the lungs). The aims were to separate malignant cells from reactive ones, and malignant mesothelioma (MM) from metastatic cancer. Asbestos exposure was not studied. Of 70 effusions collected from 2006 to 2009, 68 were analyzed. Final diagnoses were 21 MM, 29 metastatic cancer and 18 benign. All 18 benign effusions were diploid by the study's algorithm, which did not count uniformly polyploid reactive cells as abnormal. Of 50 malignant cases, 49 met the test's criteria. One MM met them only through complete loss of the 9p21 signal, and the one missed case was an MM. The test flagged all 21 malignancies with inconclusive or benign cytology. Loss of both copies of 9p21, which carries the p16INK4A gene, occurred in 12 of 21 MMs and 2 of 29 other malignancies. The authors concluded the test raised sensitivity to almost 100% without affecting specificity. They also concluded that the 9p21 deletion indicates MM but is not conclusive. They noted that more tumor-free effusions are needed to rule out false positives.

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: Diagnostic test study: laboratory adaptation and clinical evaluation of a commercial FISH test on pleural effusion samples, compared with independently verified final diagnoses
• Who was studied: 70 pleural effusions from the Department of Clinical Pathology and Cytology, Karolinska University Hospital in Huddinge, Sweden. Two were excluded for poor cell preservation. The remaining 68 were collected January 2006 to January 2009: 29 cytologically malignant, 24 inconclusive and 15 benign. Final diagnoses were 21 malignant mesothelioma, 29 metastatic cancer and 18 benign.
• Exposure: No asbestos or other exposure was studied. The factor evaluated was the UroVysion FISH test, with probes for the centromeres of chromosomes 3, 7 and 17 and for the p16INK4A gene locus at 9p21.
• Main results:
  • All 18 effusions from benign conditions were classified as diploid by the algorithm used, so there were no false positives. Reactive mesothelial cells in these samples were sometimes polyploid, most often tetraploid, for all four probes, but were not considered diagnostic of aneuploidy.
  • 49 of the 50 malignant cases met the stipulated criteria. One mesothelioma met them only by the second criterion, complete lack of the 9p21 signal. The one false negative was also a malignant mesothelioma.
  • Overall, malignancy was detected with 98% sensitivity in this material.
  • Among the 24 effusions with inconclusive cytology, aneuploidy was found in 8 of 8 mesotheliomas, 11 of 11 metastatic cancers and 0 of 5 benign cases.
  • Among the 15 cytologically benign effusions, two were aneuploid, and both turned out to be mesotheliomas.
  • Homozygous deletion of 9p21 (p16INK4A) was found in 12 of 21 malignant mesothelioma samples. It was found in 2 of 29 other malignancies (one lung adenocarcinoma, one myxofibrosarcoma).
  • In 4 of the 12 mesothelioma samples with the homozygous 9p21 deletion, benign mesothelial cells in the same sample showed a heterozygous deletion of that region.
  • The most common alterations in malignant samples were gains of chromosomes 3 and 7 (94% and 92%, respectively).
• The authors' conclusion: The authors concluded that the UroVysion FISH test can be adapted to effusions. In their view, it raises the sensitivity of effusion cytology to almost 100% by finding cancer cells in inconclusive cases, without affecting specificity.
• Limitations the authors state:
  • A larger series of tumor-free effusions is needed before the risk of false positive results can be completely ruled out.
  • Sensitivity depends on diagnostic cells being present in the sample, so false negatives cannot be completely avoided.
  • Trypsin digestion, used to break up cell groups, may damage nuclear morphology and fragment the FISH signals.
  • The 9p21 deletion was also found in a metastatic cancer and a sarcoma, so the authors regard it as an indication, not proof, of mesothelioma.
  • The lower frequency of p16INK4A deletion than reported elsewhere may reflect the size of the probe DNA, which can still bind next to shorter deletions.

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: Cytology, Mesothelial Cells, Malignant Mesothelioma, Fluorescence In Situ Hybridization (FISH), Homozygous Deletion, Pleural Effusion, Mesothelioma, Reactive Cells.

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