Malignant Mesothelioma Versus Metastatic Carcinoma of the Pleura: A CT Challenge

Our plain-English summary of Malignant Mesothelioma Versus Metastatic Carcinoma of the Pleura: A CT Challenge, by M. Bakhshayesh Karam, S. Karimi, L. Mosadegh, et al (Iranian Journal of Radiology, 2016).

The study

• Authors: M. Bakhshayesh Karam, S. Karimi, L. Mosadegh, S. Chaibakhsh
• Journal: Iranian Journal of Radiology
• Published: 2016;13(1):e10949
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant pleural mesothelioma (MPM) is a rare malignant neoplasm of the pleura that typically affects individuals occupationally exposed to asbestos through a variety of industries. MPM presents with several CT features similar to more common pleural diseases such as metastatic pleural malignancy.

Objectives: The aim of this study is to differentiate malignant pleural mesothelioma from metastatic carcinoma of the pleura by pathological and radiological assessment in order to investigate accuracy of CT scan in this regard and to compare CT features of these two malignancies.

Patients And Methods: Chest CT scans of 55 pleural malignancy patients including MPM and metastatic pleural malignancy were evaluated in this retrospective study. The pathologist made the definite diagnosis based on immunohistochemistry. A chest radiologist unaware of the pathology diagnosis observed all CT scans. Several parameters including pleural thickening, pleural effusion, thickening of inter lobar fissure, contralateral extension, contraction of involved hemithorax, parenchymal involvement (infiltration, nodules, fibrosis), pleural mediastinal involvement, lymphadenopathy, extrapleural invasion (hepatic, chest wall, diaphragm, intraperitoneal), and pericardial involvement were checked. Data analysis was carried out using SPSS version 16, and the ability of CT scan to differentiate malignant pleural mesothelioma and metastatic pleural diseases was investigated.

Results: Totally 29 males and 26 females were assessed in this study. Based on pathology, 17 MPM and 38 metastatic pleural malignancies were diagnosed. According to CT study, about 82% of the patients with MPM and about 79% of the patients with metastatic pleural diseases were correctly diagnosed by a radiologist. The most common findings suggestive of MPM were pleural thickening (88.2%), loculated effusion (58.8%), and thickening of the interlobar fissure (47.1%). Whereas free pleural effusion (71.7%), parenchymal infiltration (65.8%) and pleural thickening (63.2%) were most prevalent parameters among metastatic cases.

Conclusion: CT scan is highly accurate in differentiating malignant pleural mesothelioma and metastatic pleural diseases. Pleural thickening and thickening of interlobar fissure lead us to the diagnosis of MPM and massive free pleural effusion is more commonly seen in metastatic pleural malignancy.

In plain English

This retrospective study, from a chronic respiratory center in Iran, examined chest CT scans of 55 patients with cancer of the pleura (the lining around the lungs) who were hospitalized from 2009 through 2012. Pathology tests identified 17 patients with malignant pleural mesothelioma and 38 with metastatic carcinoma, meaning cancer that had spread to the pleura from elsewhere. A chest radiologist who did not know the pathology results read each scan and gave a most probable diagnosis. The radiologist correctly identified 14 of the 17 mesothelioma cases (82%) and 30 of the 38 metastatic cases (given as 79% in one place and 80% in another). In the mesothelioma group, the most common findings were pleural thickening (88.2%), loculated effusion (58.8%) and thickening of the interlobar fissure (47.1%). In the metastatic group, they were free pleural effusion (71.7%), parenchymal infiltration (65.8%) and pleural thickening (63.2%). The study did not report on patients' asbestos exposure. The authors concluded that CT is highly accurate in telling these two cancers apart. In their view, pleural thickening and fissure thickening point toward mesothelioma, while massive free pleural effusion is more common in metastatic disease.

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 study comparing CT readings by one chest radiologist, who was unaware of the pathology diagnosis, against pathology and immunohistochemistry as the gold standard
• Who was studied: 55 patients with pleural malignancy (29 males, 26 females), hospitalized from 2009 through 2012 at a chronic respiratory center in Iran. By pathology, 17 had malignant pleural mesothelioma and 38 had metastatic carcinoma of the pleura.
• Exposure: The study did not measure or report asbestos exposure. It compared CT scan features (such as pleural thickening, pleural effusion, interlobar fissure thickening, parenchymal involvement and invasion of nearby organs) between pleural mesothelioma and metastatic pleural carcinoma.
• Main results:
  • Pathology diagnosed 17 patients with mesothelioma and 38 with metastatic pleural malignancy.
  • The radiologist correctly diagnosed 14 of 17 mesothelioma cases and 30 of 38 metastatic cases.
  • The correct-diagnosis rates were 82% for the mesothelioma group and 79% (stated as 80% in the discussion) for the metastatic group.
  • In the mesothelioma group, the most common CT findings were pleural thickening (88.2%), loculated effusion (58.8%) and thickening of the interlobar fissure (47.1%).
  • In the metastatic group, the most common CT findings were free pleural effusion (71.7%), parenchymal infiltration (65.8%) and pleural thickening (63.2%). Effusion in this group was mostly massive rather than mild or moderate (55.3% vs. 15.8%).
  • Pleural thickening (P = 0.05) and thickening of the interlobar fissure (P = 0.02) were more prevalent in mesothelioma than in metastatic carcinoma.
  • Free pleural effusion (P = 0.01), massive pleural effusion (P = 0.003) and parenchymal infiltration (P = 0.03) were significantly more common in metastatic pleural disease than in mesothelioma.
  • Invasion of the chest wall, liver and peritoneum was rare overall but more common in mesothelioma. Chest wall invasion was 11.8% in mesothelioma vs 2.6% in metastatic cases, hepatic invasion 5.9% vs 0, and intraperitoneal invasion 17.6% vs 2.6%.
• The authors' conclusion: The authors concluded that CT scan is highly accurate in differentiating malignant pleural mesothelioma from metastatic pleural disease. In their view, pleural thickening and thickening of the interlobar fissure point to mesothelioma, while massive free pleural effusion points to metastatic carcinoma.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Carcinoma, Pleura, Pleural Mesothelioma, Neoplasm, CT Scan, Immunohistochemistry, Pathology.

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