Malignant pleural mesothelioma showing rare morphology indistinguishable from myxofibrosarcoma concomitant with EGFR-mutated lung adenocarcinoma: A case report

Our plain-English summary of Malignant pleural mesothelioma showing rare morphology indistinguishable from myxofibrosarcoma concomitant with EGFR-mutated lung adenocarcinoma: A case report, by H. Onagi, T. Hayashi, T. Saito, et al (International Journal of Surgery Case Reports, 2021).

The study

• Authors: H. Onagi, T. Hayashi, T. Saito, S. Kishikawa, K. Takamochi, K. Suzuki
• Journal: International Journal of Surgery Case Reports
• Published: 2021;85:106237
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction And Importance: Primary tumors of the pleura are rare, with malignant mesothelioma being the most common of these neoplasms. Pathological diagnosis of sarcomatoid mesothelioma can be more challenging than that of epithelioid malignant mesothelioma because of its similarities with true sarcomas and restricted or inconsistent expression of mesothelial markers in immunohistochemistry analysis.

Presentation Of Case: Here, we present an unusual case of malignant pleural mesothelioma concomitant with lung adenocarcinoma in a 72-year-old Japanese man, a smoker with no family history of cancer and asbestos exposure. Malignant pleural mesothelioma is composed of epithelial and spindle-shaped cells. Spindle-shaped cells with scant eosinophilic cytoplasm and hyperchromatic nuclei proliferated in abundant myxoid stroma containing thin-walled blood vessels, mimicking myxofibrosarcoma. The loss of BAP1 (BRCA1-associated protein 1) expression, as assessed by immunohistochemistry, and homozygous deletions of CDKN2A, detected using fluorescence in situ hybridization (FISH), were observed in both components. Targeted sequencing revealed that lung adenocarcinoma harbored EGFR mutations, whereas no mutations were detected in either component of biphasic mesothelioma.

Discussion: Although alcian blue-stained mucins were detected in biphasic mesothelioma subsets, the clinicopathological significance of myxoid stroma in biphasic and sarcomatoid mesothelioma remains largely unknown.

Conclusion: Our case presented a unique morphology mimicking myxofibrosarcoma in a sarcomatoid component of biphasic mesothelioma; therefore, it raises a question on the clinicopathological significance of myxoid stroma in sarcomatous areas of biphasic and sarcomatoid mesothelioma.

Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.

In plain English

This case report from Juntendo University in Tokyo described one patient: a 72-year-old Japanese man, a smoker (53 pack-years), who came to hospital with a cough. The authors reported no family history of cancer or asbestos exposure, and no asbestos bodies were found in the tissue. A wedge resection removed a 15 mm lung nodule and nodules on the lung lining (visceral pleura). The pleural tumor was diagnosed as biphasic pleural mesothelioma, made of epithelial and spindle-shaped cells. The spindle-cell part, in a jelly-like (myxoid) background, looked like a soft-tissue cancer called myxofibrosarcoma. Both parts showed loss of BAP1 protein on staining and homozygous deletions of the CDKN2A gene, meaning both copies were missing. The lung nodule was a separate adenocarcinoma with an EGFR mutation. No mutations were found in the mesothelioma, though the gene panel did not test BAP1. Seven months after surgery the patient was alive with no recurrence. The authors concluded the case raises a question about the significance of myxoid stroma in mesothelioma, and wrote that screening for inherited BAP1 changes might be needed.

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 72-year-old Japanese man, a smoker (53 pack-years), seen with a cough at the authors' hospital (Juntendo University, Tokyo); history of diabetes mellitus and dyslipidemia
• Exposure: No asbestos exposure was reported for this patient, and asbestos bodies were not detected in the examined tissue; the patient was a smoker (53 pack-years). No fiber type is named.
• Main results:
  • The visceral pleural tumor had two components, epithelial and spindle-shaped cells, each making up more than 10% of the tumor.
  • The spindle-shaped cells grew in myxoid stroma with thin-walled blood vessels, mimicking myxofibrosarcoma.
  • Asbestos bodies were not detected in the tumor tissue examined.
  • Epithelial cells stained positive for mesothelial and other markers, including calretinin, mesothelin, D2–40 and HEG-1. Spindle-shaped cells were negative for all of these except D2–40.
  • Immunohistochemical staining showed loss of BAP1 expression in both components of the pleural tumor.
  • FISH showed homozygous deletions of CDKN2A in both components of the pleural tumor.
  • No SS18-SSX fusion was found, which excluded synovial sarcoma.
  • The pleural tumor was diagnosed as diffuse pleural mesothelioma, biphasic subtype.
  • The lung nodule was a separate papillary adenocarcinoma, which retained BAP1 expression.
  • Sequencing found an EGFR (L858R) mutation at 13% allelic frequency in the lung adenocarcinoma. No mutations were detected in either component of the biphasic mesothelioma.
  • The patient was alive and well with no evidence of recurrence 7 months after surgery.
• The authors' conclusion: The authors concluded that the myxofibrosarcoma-like morphology in the sarcomatoid component raises a question about the clinicopathological significance of myxoid stroma in sarcomatous areas of biphasic and sarcomatoid mesothelioma. They also wrote that screening for germline BAP1 status might be needed.
• Limitations the authors state:
  • The gene panel used did not include BAP1, so it was unclear whether the tumor cells had BAP1 mutations.
  • The authors could not determine whether the patient carried a germline (inherited) BAP1 mutation.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, EGFR, Lung Adenocarcinoma, Pleura, Malignant Mesothelioma, Neoplasm, Sarcomatoid, Mesothelioma.

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