Pseudomesotheliomatous lung cancer mimicking mesothelioma on ¹⁸F-FDG PET/CT images: report of 2 cases

Our plain-English summary of Pseudomesotheliomatous lung cancer mimicking mesothelioma on ¹⁸F-FDG PET/CT images: report of 2 cases, by T. Nakamori, S. Kosuda, Y. Kyoto, et al (Japanese Journal of Radiology, 2013).

The study

• Authors: T. Nakamori, S. Kosuda, Y. Kyoto, A. Fujikawa, Y. Naoi, Y. Nakamori
• Journal: Japanese Journal of Radiology
• Published: 2013;31(8):542-5
• Type of article: Case report
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The authors report two cases of pseudomesotheliomatous lung cancer (PLC) detected by (18)F-FDG PET/CT scan. (18)F-FDG PET/CT clearly revealed the extent of the disease in both cases, a case of adenocarcinoma of the lung and a case of squamous cell carcinoma of the lung. Intense (18)F-FDG uptake by the diffusely thickened pleurae and primary lesion was observed in both cases, and increased (18)F-FDG uptake by a pelvic bone metastasis was observed in the case of squamous cell carcinoma. Although PLC is indistinguishable from malignant pleural mesothelioma on (18)F-FDG PET/CT scans, (18)F-FDG PET/CT was helpful in identifying the primary focus of the PLCs and in staging the disease. Diagnostic image interpreters should be familiar with the (18)F-FDG PET/CT findings in PLC.

In plain English

This article reported two cases of pseudomesotheliomatous lung cancer, by authors at hospitals in Japan. This is a lung cancer that spreads widely over the pleura (the lining around the lung) and can look like malignant pleural mesothelioma. Both patients were men, aged 76 (74 in one figure caption) and 80, and both were first suspected of having mesothelioma. They had smoking histories of 40 and 50 pack-years, and neither had a known history of exposure to asbestos products. Each had an 18F-FDG PET/CT scan read at 1 and 2 hours. In both men, the thickened pleura and the main tumour took up the tracer intensely, resembling mesothelioma, and uptake values were over 10.0 on the 2-hour images. Biopsy showed adenocarcinoma of the lung in the first man, with staining negative for calretinin and thrombomodulin. It showed squamous cell carcinoma of the lung in the second man, whose scan also showed spread to the pelvic bone. The authors concluded that this cancer was difficult to tell apart from malignant pleural mesothelioma on these scans. They found the scan helpful in locating the primary tumour and staging the 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: case report (2 cases)
• Who was studied: Two men, both initially suspected of having mesothelioma. Case 1 had a 3-month history of breathlessness; the case narrative gives his age as 76, but the Figure 1 caption gives 74. Case 2 was 80, with a 3-month history of cough, breathlessness and pleuritic chest pain. The authors' departments are in Japan. No dates of the cases are given.
• Exposure: Neither patient had a known history of exposure to asbestos products. Both had cigarette smoking histories, printed as 40 pack/year (case 1) and 50 pack/year (case 2). The study's subject was the appearance of the disease on 18F-FDG PET/CT scans, not asbestos exposure.
• Main results:
  • In both patients, intense tracer uptake by the thickened pleura and the primary lesion mimicked the uptake seen in malignant pleural mesothelioma.
  • Case 1: SUVmax values at 1 hour and 2 hours were 15.1 to 18.2 for the primary focus and 9.5 to 12.4 for the thickened pleura. No distant metastasis was seen.
  • Case 1: the biopsy was diagnosed as adenocarcinoma of the lung, and immunohistochemical staining was negative for calretinin and thrombomodulin.
  • Case 2: SUVmax values at 1 hour and 2 hours were 11.7 to 14.9 for the primary focus and 8.3 to 10.8 for the pleura. A distant metastasis in the pelvic bone was detected.
  • Case 2: the biopsy was diagnosed as squamous cell carcinoma of the lung.
  • In both patients, SUVmax values were higher on the 2-hour (delayed) images than on the 1-hour images, and over 10.0 on the delayed images.
• The authors' conclusion: The authors concluded that it is difficult to distinguish pseudomesotheliomatous lung cancer from malignant pleural mesothelioma using 18F-FDG PET/CT uptake patterns and SUVmax values. They also stated that the scan is helpful in identifying the primary focus and staging the disease.

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: Lung Cancer, Mesothelioma, CT Scan, Adenocarcinoma, Squamous Cell Carcinoma, Metastasis, Pleural Mesothelioma, Staging.

Related studies

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• Prognostic value of 18F-FDG standard uptake value by integrated PET/CT in the staging of malignant pleural mesothelioma — G. Genestreti, A. Moretti, et al. (2012)
• ¹⁸F-fluorodeoxyglucose PET/CT findings in pleural effusions of patients with known cancer. A cytopathological correlation — I. Letovanec, G. Allenbach, et al. (2012)
• Sarcomatoid carcinoma (carcinosarcoma) of the lung mimics malignant pleural mesothelioma on 18F-FDG PET/CT: a report of 2 cases — A. Ciarallo, W. Makis, et al. (2012)
• Multiple primary hepatic malignant mesotheliomas mimicking cystadenocarcinomas on enhanced CT and FDG PET/CT — A. Dong, H. Dong, et al. (2014)

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