Malignant pleural mesothelioma: visual assessment by using pleural pointillism at diffusion-weighted MR imaging

Our plain-English summary of Malignant pleural mesothelioma: visual assessment by using pleural pointillism at diffusion-weighted MR imaging, by J. Coolen, F. De Keyzer, P. Nafteux, et al (Radiology, 2015).

The study

• Authors: J. Coolen, F. De Keyzer, P. Nafteux, W. De Wever, C. Dooms, J. Vansteenkiste, A. Derweduwen, I. Roebben, E. Verbeken, P. De Leyn, D. Van Raemdonck, K. Nackaerts, S. Dymarkowski, J. Verschakelen
• Journal: Radiology
• Published: 2015;274(2):576-84
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To evaluate the diagnostic accuracy of the visual assessment of malignant pleural mesothelioma (MPM) on magnetic resonance (MR) images by using two known visual markers (mediastinal pleural thickness and shrinking of the lung) and a newly introduced one (pleural pointillism).

Materials And Methods: With the approval of the local ethics committee, 100 consecutive patients (mean age, 61.4 years; age range, 18-87 years; 75 men, 25 women) suspected of having MPM pleural abnormalities underwent positron emission tomography/computed tomography and MR imaging, including diffusion-weighted (DW) MR imaging, followed by explorative thoracoscopy or guided biopsy with histopathologic confirmation. Because visual assessment is still the preferred method of image interpretation, the diagnostic accuracy of mediastinal pleural thickening, shrinking lung (hemithorax volume decrease due to fibrosis), and pleural pointillism were examined. Pleural pointillism was denoted by the presence of multiple, hyperintense pleural spots on high-b-value DW images. Histopathologic findings in the surgical specimen served as the reference standard. McNemar tests with Bonferroni correction were used to assess differences in accuracy among the three examined markers.

Results: Of 100 patients, 33 had benign pleural alterations, and 67 had malignant pleural diseases (MPDs); 57 of 67 had MPM. A total of 78 patients received a correct diagnosis (benign vs malignant) on the basis of mediastinal pleural thickening (sensitivity, 81%; specificity, 73%; accuracy, 78%); and 66 patients, on the basis of shrinking lung (sensitivity, 60%; specificity, 79%; accuracy, 66%). The correct diagnosis was indicated on the basis of pleural pointillism in 88 patients (sensitivity, 93%; specificity, 79%; accuracy, 88%).

Conclusion: Visual assessment of pleural pointillism on high-b-value DW images is useful to differentiate MPD from benign alterations, performing substantially better than mediastinal pleural thickness and shrinking lung, and might obviate unnecessary invasive procedures for MPM.

© RSNA, 2014.

In plain English

This prospective study at University Hospitals Leuven, Belgium, examined 100 patients with pleural disease suspected to be malignant pleural mesothelioma, enrolled between November 2009 and December 2012. The authors tested a new MR imaging sign, "pleural pointillism": multiple bright pleural spots on high-b-value diffusion-weighted images. They compared it with two CT signs, mediastinal pleural thickening and shrinking lung, against tissue diagnosis. Tissue diagnosis showed malignant pleural disease in 67 patients, 57 of them mesothelioma. The other 33 had benign conditions such as pleural plaques or pleuritis. Pointillism correctly classified 88 of 100 patients (accuracy 88.0%, 95% confidence interval 80.2 to 93.0%), with sensitivity 92.5% (83.7 to 96.8%) and specificity 78.8% (62.2 to 89.3%). Mediastinal thickening classified 78 correctly and shrinking lung 66. Pointillism did significantly better than shrinking lung. Its difference from mediastinal thickening (P = .23) was not statistically significant. The authors concluded that pointillism seems a reasonably accurate tool for diagnosing malignant pleural disease and that larger studies are needed. They noted it may be less specific outside a group of suspected mesothelioma patients. The study did not examine asbestos exposure.

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: Prospective diagnostic accuracy study comparing three visual imaging signs against histopathology
• Who was studied: 109 consecutive patients with pleural disease suspected of malignant pleural mesothelioma were enrolled at University Hospitals Leuven, Belgium, between November 2009 and December 2012. Nine were excluded, leaving 100 (75 men, 25 women; mean age 61.4 years, range 18 to 87).
• Exposure: Not reported. The study did not assess asbestos or other exposures. It evaluated imaging signs: pleural pointillism on diffusion-weighted MR images (b value 1000), and mediastinal pleural thickening and shrinking lung assessed on CT images.
• Main results:
  • 67 of 100 patients had malignant pleural disease: 57 mesothelioma and 10 metastatic disease. 33 had benign tumors, alterations or inflammatory disorders (for example solitary fibrous tumor, pleural plaques, talc pleurodesis, pleuritis).
  • Pleural pointillism: sensitivity 92.5% (62 of 67 malignant cases; 95% confidence interval 83.7 to 96.8%)
  • Pleural pointillism: specificity 78.8% (26 of 33 benign cases; 95% confidence interval 62.2 to 89.3%)
  • Pleural pointillism: accuracy 88.0% (88 of 100; 95% confidence interval 80.2 to 93.0%)
  • Pleural pointillism: positive predictive value 90% (62 of 69), negative predictive value 84% (26 of 31)
  • Pleural pointillism was present in 96.5% (55 of 57) of patients with mesothelioma
  • Mediastinal pleural thickening: sensitivity 80.6% (54 of 67; 95% confidence interval 69.6 to 88.3%), specificity 72.7% (24 of 33; 55.8 to 84.9%), accuracy 78% (78 of 100)
  • Shrinking lung: sensitivity 59.7% (40 of 67; 95% confidence interval 47.7 to 70.6%), specificity 78.8% (26 of 33; 62.2 to 89.3%), accuracy 66% (66 of 100)
  • After Bonferroni correction, accuracy differed significantly between pointillism and shrinking lung (P less than .001). The differences between mediastinal thickening and pointillism (P = .23) and between mediastinal thickening and shrinking lung (P = .13) were not statistically significant.
  • Interobserver agreement (kappa) between the two readers was 0.71 for mediastinal thickening, 0.48 for lung shrinkage and 0.53 for pleural pointillism
• The authors' conclusion: The authors concluded that visual assessment of pleural pointillism on high-b-value diffusion-weighted images seems to be a reasonably accurate tool for diagnosing malignant pleural disease. They said it might guide biopsy and eventually help avoid invasive procedures, and that larger studies are needed to validate its clinical use and specificity.
• Limitations the authors state:
  • Relatively small number of patients, because the condition is rare
  • Only patients suspected of having mesothelioma were included, so results may be biased. The authors expected pointillism to be less specific in a more general patient population.
  • Relatively low interobserver agreement for the pointillism assessment, which the authors attributed to the second reader's lower experience with diffusion-weighted images

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: Pleural Mesothelioma, Pleural Thickness, Thoracoscopy, Biopsy, Pleural Thickening, Hemithorax, Fibrosis.

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