A Case of Solitary Well-Differentiated Papillary Mesothelioma with Invasive Foci in the Pleura

Our plain-English summary of A Case of Solitary Well-Differentiated Papillary Mesothelioma with Invasive Foci in the Pleura, by S. Shimizu, H.E. Yoon, N. Ito, et al (Pathology International, 2017).

The study

• Authors: S. Shimizu, H.E. Yoon, N. Ito, T. Tsuji, Y. Funakoshi, T. Utsumi, M. Sakaguchi, T. Tsujimura, T. Kasai, K. Hiroshima, A. Matsumura
• Journal: Pathology International
• Published: 2017;67(1):45-49
• Type of article: Case report
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Well-differentiated papillary mesothelioma (WDPM) is a rare, distinct tumor consisting of mesothelial cells with a papillary architecture, bland cytological features, and a tendency toward superficial spread without invasion. Rare cases with superficial invasion are termed WDPM with invasive foci. We report a case of solitary WDPM with invasive foci in the pleura. A 61-year-old woman presented with a lung adenocarcinoma. A small papillary lesion measuring 29 × 10 × 8 mm was incidentally found in the parietal pleura during a lobectomy for the lung adenocarcinoma. The fibrovascular core of the small papillary lesion was surrounded by a single layer of cuboidal cells with mild to moderate atypia and large nucleoli. Atypical mesothelial cells focally invaded the submesothelial layer. The cells of the papillary lesion were positive for cytokeratins and mesothelial markers. The Ki67 index was <1 %. The lesion did not show p16 loss on fluorescence in situ hybridization. We could not detect atypical mesothelial cells in the specimen from an extrapleural pneumonectomy. WDPM with invasive foci is prone to multifocality; however, our case represents a solitary case in the pleura.

© 2016 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.

In plain English

This Japanese case report describes one patient. A 61-year-old woman with no history of asbestos exposure had surgery for a lung adenocarcinoma, a type of lung cancer. During the operation, surgeons found by chance a small papillary lesion, 29 × 10 × 8 mm, on the part of the parietal pleura (chest lining) facing the mediastinum, the center of the chest. Microscopically it was covered by a single layer of mesothelial cells with mild to moderate atypia (abnormal-looking cells). In small areas these cells had invaded the layer beneath the surface. Stains matched mesothelial cells. A cell-growth marker (Ki67) was below 1%, and genetic testing showed no p16 deletion. The authors diagnosed well-differentiated papillary mesothelioma (WDPM) with invasive foci. Because malignant mesothelioma could not be ruled out, surgeons then removed the lung together with its pleura (extrapleural pneumonectomy). No atypical mesothelial cells were found in that tissue, but a small spread of the lung cancer was. The WDPM did not recur for more than three years. The authors concluded that such tumors are usually multiple, but a solitary one can occur in the pleura.

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 61-year-old woman treated at the National Hospital Organization Kinki-chuo Chest Medical Center, Japan, for lung adenocarcinoma
• Exposure: No asbestos exposure: the article states the patient had no history of asbestos exposure
• Main results:
  • A pleural lesion was found incidentally during lobectomy for lung adenocarcinoma, in the parietal pleura of the lateral aspect of the mediastinum
  • The pleural lesion measured 29 × 10 × 8 mm
  • The lesion was covered by a single layer of cuboidal mesothelial cells with mild to moderate atypia, without mitotic figures or necrosis
  • Atypical mesothelial cells focally invaded the submesothelial layer
  • The lesion's cells were positive for cytokeratins, BAP-1 and mesothelial markers including calretinin, and negative for adenocarcinoma markers. The Ki67 index was less than 1%.
  • Fluorescence in situ hybridization showed no p16 deletion in the lesion (normal pattern 68.0%, hemizygous deletion pattern 28.0%, homozygous deletion pattern 4.0%)
  • The extrapleural pneumonectomy specimen showed a 5-mm disseminated lung adenocarcinoma in the parietal pleura but no atypical mesothelial cells in the parietal or visceral pleura
  • The WDPM with invasive foci had not recurred for more than three years. The lung adenocarcinoma metastasized two years after surgery and was controlled with gefitinib.
• The authors' conclusion: The authors concluded that WDPM with invasive foci is prone to multifocality, but this case shows that a solitary lesion can also occur in the pleura. They state it is, to their knowledge, the first such report.
• Limitations the authors state:
  • The authors state it was impossible to distinguish WDPM with invasive foci from malignant mesothelioma with a WDPM-like pattern by morphology alone
  • The authors state that further study of lesion sizes and of immunohistochemistry markers is needed to tell these lesions apart

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: Well-Differentiated Papillary Mesothelioma, Pleura, Mesothelial Cells, Lung Adenocarcinoma, Parietal Pleura, Fluorescence In Situ Hybridization (FISH), Extrapleural Pneumonectomy (EPP).

Related studies

• Well-differentiated papillary mesothelioma with invasive foci — A. Churg, T. Allen, et al. (2014)
• Simultaneous occurrence of a rectal carcinoma and a diffuse well differentiated papillary mesothelioma of the peritoneum — G.R. Jatzko, J. Jester (1997)
• Combined adenomatoid tumor and well differentiated papillary mesothelioma of the omentum — Y. Hatano, Y. Hirose, et al. (2011)
• BAP1 loss is unusual in well-differentiated papillary mesothelioma and may predict development of malignant mesothelioma — H.E. Lee, J.R. Molina, et al. (2018)
• Well-differentiated papillary mesothelioma: peritoneal implants are not always metastases in the presence of cancer — G.W. Irwin, A. Ervine, et al. (2014)
• Peritoneal well-differentiated papillary mesothelioma coexisting with endometrial adenocarcinoma mimicking peritoneal carcinomatosis: A case report — Y.Y. Chen, P.C. Li, et al. (2020)

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