Extensive Skeletal Muscle Metastases in Malignant Pleural Mesothelioma Detected by FDG PET/CT

Our plain-English summary of Extensive Skeletal Muscle Metastases in Malignant Pleural Mesothelioma Detected by FDG PET/CT, by M. Yilmaz, O. Kandemir, E. Tutar (World Journal of Nuclear Medicine, 2023).

The study

• Authors: M. Yilmaz, O. Kandemir, E. Tutar
• Journal: World Journal of Nuclear Medicine
• Published: 2023;22(4):293-296
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant pleural mesothelioma (MPM) is a rare but aggressive tumor originating from pleural mesothelial cells. Distant skeletal muscle metastasis is rare in MPM. A 54-year-old woman was diagnosed with epithelioid MPM and treated with surgery, chemotherapy, and radiotherapy 2 years ago. During follow-up, diffuse irregular pleural thickening with focal chest wall invasion in the right hemithorax and two small pleural thickenings in the left hemithorax were seen on control diagnostic contrast-enhanced computed tomography (CECT). Fluorine-18 fluorodeoxyglucose positron emission tomography/CT (FDG PET/CT) imaging was performed as part of restaging. PET showed diffusely increased FDG uptake in the recurrent right pleural tumor, and two hypermetabolic small metastatic foci in the contralateral pleura. In addition, multiple hypermetabolic areas of various sizes in various skeletal muscle localizations, suggestive of extensive muscle metastases were noted. Histopathologic study confirmed metastatic epithelioid MPM. FDG PET/CT revealed multiple muscle metastases which were not observed on earlier CECT and contributed to the visualization of more extensive metastatic involvements in the presented case with MPM. FDG PET/CT can detect rarely seen skeletal muscle metastases that are not visualized on diagnostic CT, and provides more accurate restaging of MPM.

The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. ( https://creativecommons.org/licenses/by/4.0/ ).

In plain English

This article was a case report. It described a 54-year-old woman diagnosed with epithelioid malignant pleural mesothelioma two years earlier and treated with right extrapleural pneumonectomy, hyperthermic intrathoracic chemotherapy, and radiotherapy. The report did not describe her asbestos exposure. After she complained of right-sided chest pain, a CT scan showed irregular pleural thickening with focal chest wall invasion on the right and two small pleural thickenings on the left. An FDG PET/CT scan two weeks later showed high uptake in the recurrent right pleural tumor (SUVmax 13.4) and two small foci in the left pleura (SUVmax 2.7). It also showed many areas of uptake in skeletal muscles, most extensive in both legs (SUVmax between 3.4 and 18.5). When the contrast-enhanced CT was reviewed again, it showed no lesions at those muscle sites. On examination, her only muscle finding was slight swelling and mild pain in the right biceps. A biopsy from the left calf confirmed metastatic epithelioid mesothelioma. The authors concluded that rare muscle metastases may be missed on contrast-enhanced CT but that FDG PET/CT can detect them and provides more accurate restaging.

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 (single patient)
• Who was studied: One 54-year-old woman with epithelioid malignant pleural mesothelioma diagnosed 2 years earlier, previously treated with right extrapleural pneumonectomy, hyperthermic intrathoracic chemotherapy, and radiotherapy; authors based in Turkey
• Exposure: Not reported for this patient; the article does not describe any asbestos exposure history for her
• Main results:
  • Control CT (prompted by right-sided chest pain) showed diffuse irregular pleural thickening with focal chest wall invasion in the right hemithorax and two small pleural thickenings in the left hemithorax
  • FDG PET/CT showed high uptake in the recurrent right pleural tumor with SUVmax of 13.4
  • Two small hypermetabolic foci in the left pleura, suggesting metastatic disease to the contralateral pleura, had SUVmax of 2.7
  • Multiple hypermetabolic areas were seen in skeletal muscles (left medial pterygoid, paraspinal muscles, both gluteal muscles, right biceps brachii, and numerous muscles of both thighs and calves), with SUVmax between 3.4 and 18.5
  • On re-review of the contrast-enhanced CT, no contrast-enhanced lesions were seen at the sites of the hypermetabolic muscle lesions
  • On physical examination the patient had only slight swelling with mild pain in the lower right biceps brachii muscle
  • Biopsy of a muscle lesion in the left calf confirmed metastatic epithelioid malignant pleural mesothelioma
  • The tumor cells stained positive for CK 5/6, WT-1, CK7 and CK20, and negative for calretinin, thyroid transcription factor-1, carcinoembryonic antigen and CDX-2
• The authors' conclusion: The authors concluded that rarely seen muscle metastases in malignant pleural mesothelioma may be missed on diagnostic contrast-enhanced CT, but FDG PET/CT can detect unusual or unexpected distant metastases such as skeletal muscle metastases and provides more accurate restaging

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Mesothelial Cells, Metastasis, Epithelioid, Chemotherapy, Pleural Thickening, Hemithorax, Contralateral Pleura.

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