Accuracy of diagnostic biopsy for the histological subtype of malignant pleural mesothelioma

Our plain-English summary of Accuracy of diagnostic biopsy for the histological subtype of malignant pleural mesothelioma, by S.C. Kao, T.D. Yan, K. Lee, et al (Journal of Thoracic Oncology, 2011).

The study

• Authors: S.C. Kao, T.D. Yan, K. Lee, J. Burn, D.W. Henderson, S. Klebe, C. Kennedy, J. Vardy, S. Clarke, N. van Zandwijk, B.C. McCaughan
• Journal: Journal of Thoracic Oncology
• Published: 2011;6(3):602-5
• Cited by: 44 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: Histological subtype is an established prognostic factor in malignant pleural mesothelioma (MPM). We retrospectively investigated the accuracy of classifying histological subtype on diagnostic biopsies and examined the impact of different diagnostic procedures on the outcome.

Methods: Consecutive patients with histologically confirmed MPM who underwent extrapleural pneumonectomy (EPP) from 1994 to 2009 were included. Patient records were reviewed, and the initial diagnoses of histological subtype were obtained. The archival EPP specimens were reviewed by a panel of pathologists. The histological subtype obtained at review was compared with the initial diagnosis.

Results: Eighty-five patients underwent EPP. Two patients achieved a pathological complete response after neoadjuvant chemotherapy, leaving 83 patients to be included in this review. Different diagnostic methods were used before EPP: 81% thoracoscopy; 7% thoracotomy; 11% computed tomography-guided procedure; and 1% other. Patients determined to have an epithelial subtype (n = 64) at EPP were diagnosed correctly at initial diagnostic biopsy in 84% of cases, whereas patients considered to have a biphasic subtype (n = 19) at EPP were diagnosed correctly at diagnostic biopsy in 26% of cases. The sensitivity and specificity of diagnostic biopsy for epithelial MPM was 93% and 31%, respectively. The overall subtype misclassification rate was 20%. Biopsy by thoracotomy was most accurate in subtype classification (83%) compared with thoracoscopy (74%) and computed tomography-guided procedure (44%).

Conclusions: The determination of histological subtype from a diagnostic biopsy is difficult due to sampling error, but an adequate specimen obtained from surgical biopsy increases the accuracy of subtype classification compared with radiological-guided biopsies.

In plain English

This retrospective study from two Sydney hospitals examined how accurately a diagnostic biopsy identified the histological subtype of malignant pleural mesothelioma. It included consecutive patients who had extrapleural pneumonectomy between 1994 and 2009. Eighty-three of 85 patients were analyzed; two had no remaining tumor after preoperative chemotherapy. Pathologists who did not know the original diagnosis reviewed 78 surgical specimens. For five patients whose tissue could not be found, the subtype came from the pathology report. These served as the reference. At surgery, 64 patients had epithelial and 19 had biphasic mesothelioma. Of the 64 epithelial cases, 54 (84%) had been called epithelial at biopsy. Of the 19 biphasic cases, 5 (26%) had been called biphasic and 11 (58%) epithelial. Among patients whose biopsy had assigned a subtype, 20% were misclassified. Subtype accuracy was 83% for thoracotomy biopsies, 74% for thoracoscopy and 44% for CT-guided procedures, though only 9 patients had CT-guided procedures. The authors concluded that an adequate pleural biopsy increases subtyping accuracy. They cautioned against selecting patients for extrapleural pneumonectomy by biopsy subtype unless a large specimen was obtained and the subtype was judged accurate.

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 single-center review comparing the subtype at initial diagnostic biopsy with the final subtype of the surgical specimen, which served as the gold standard
• Who was studied: 85 consecutive patients with malignant pleural mesothelioma who underwent extrapleural pneumonectomy at Royal Prince Alfred and Strathfield Private Hospitals, Sydney, Australia, from 1994 to 2009. Median age was 58 years (range 22 to 74) and 80% were men. 83 patients were included in the analysis.
• Exposure: Asbestos exposure was not studied. The comparison was between diagnostic biopsy methods: thoracoscopy (81%), thoracotomy (7%), CT-guided procedure (11%) and biopsy of a chest wall nodule (1%).
• Main results:
  • Seventy-eight surgical specimens were re-examined by pathologists blinded to the original diagnosis. For the remaining five, the archival tissue could not be located, and the subtype was taken from the pathology report.
  • On final review of the surgical specimens, 64 of 83 patients (77%) had epithelial and 19 (23%) had biphasic mesothelioma.
  • Of the 64 patients with epithelial subtype at surgery, 54 (84%) had been classified as epithelial at the initial biopsy.
  • Of the 19 patients with biphasic subtype at final review, 11 (58%) had initially been classified as epithelial, 5 (26%) as biphasic and 3 (16%) were not classified.
  • For an epithelial diagnosis at initial biopsy, sensitivity was 93%, specificity 31%, positive predictive value 83% and negative predictive value 56%. These figures counted only patients whose initial biopsy assigned a subtype.
  • The overall subtype misclassification rate at initial biopsy was 20%. It applies to patients whose initial biopsy assigned a subtype; patients without an initial subtype or with a negative initial biopsy were excluded.
  • Accuracy of subtype diagnosis was 74% after thoracoscopy, 83% after biopsy at thoracotomy and 44% after a CT-guided procedure.
• The authors' conclusion: The authors concluded that an adequate pleural biopsy increases the accuracy of histological subtyping. They cautioned against using subtype as a selection criterion for extrapleural pneumonectomy unless a large diagnostic biopsy specimen was obtained and the subtype assignment was deemed accurate.
• Limitations the authors state:
  • Only a small number of patients (9) had CT-guided procedures, which the authors said may limit interpretation of those results.

Topics

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

Medical terms in this study, explained in our Lexicon: Biopsy, Histological Subtype, Pleural Mesothelioma, Extrapleural Pneumonectomy (EPP), Neoadjuvant Chemotherapy, Thoracoscopy, Thoracotomy, Biphasic Mesothelioma.

Related studies

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• Low calretinin expression and high neutrophil-to-lymphocyte ratio are poor prognostic factors in patients with malignant mesothelioma undergoing extrapleural pneumonectomy — S.C. Kao, S. Klebe, et al. (2011)
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• High SUVmax on FDG-PET indicates pleomorphic subtype in epithelioid malignant pleural mesothelioma: supportive evidence to reclassify pleomorphic as nonepithelioid histology — K. Kadota, S.S. Kachala, et al. (2012)
• Tomotherapy after pleurectomy/decortication or biopsy for malignant pleural mesothelioma allows the delivery of high dose of radiation in patients with intact lung — E. Minatel, M. Trovo, et al. (2012)

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