Pleomorphic mesothelioma: report of 10 cases

Our plain-English summary of Pleomorphic mesothelioma: report of 10 cases, by N.G. Ordóñez (Modern Pathology, 2012).

The study

• Author: N.G. Ordóñez
• Journal: Modern Pathology
• Published: 2012;25(7):1011-22
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Mesotheliomas with pleomorphic features are rare and only a few studies on this mesothelioma variant have been published. Little information regarding the immunoprofile of these tumors and none on their electron microscopic features was included in these studies. Herein are reported 10 cases of pleomorphic mesothelioma that were investigated using a large panel of immunohistochemical markers, 4 of which were also studied by electron microscopy. All of the patients were men and seven had a history of asbestos exposure. Nine of the cases originated in the pleura and one in the peritoneum. Histologically, the tumors were characterized by being composed of large, often discohesive, cells that varied in size and shape, had dense abundant eosinophilic cytoplasm, and single or multiple irregular nuclei, which often contained one or several large nucleoli. Mitotic activity was high and atypical mitoses frequent. Immunoreactivity for pan-keratin and keratin 7 was strong in all of the cases. Expression for calretinin, WT1, podoplanin, mesothelin and keratin 5/6 was also frequent, but variable. All cases were negative for MOC-31, carcinoembryonic antigen, CD15, TAG-72 and thyroid transcription factor-1. Electron microscopy often showed the presence of abundant long, slender microvilli on the cell membrane of the neoplastic cells. These findings demonstrate that, contrary to what has been suggested by some investigators, both immunohistochemistry and electron microscopy can be very helpful in assisting in the diagnosis of pleomorphic mesotheliomas. That the seven patients who underwent extrapleural pneumonectomy had extensive lymph node metastasis and that the median survival of those patients for whom follow-up information was available was only 8.2 months indicates that mesotheliomas with pleomorphic features are associated with highly aggressive clinical behavior. Therefore, when this subtype of epithelioid mesothelioma is present, it should be reported as it can significantly affect the prognosis and treatment of the patient.

In plain English

This article was a case series from the Department of Pathology at The University of Texas MD Anderson Cancer Center. The author found 10 cases of pleomorphic mesothelioma among 640 mesothelioma cases in the department's files. Pleomorphic mesothelioma is a rare form of epithelioid mesothelioma whose cells vary greatly in size and shape. The author examined all 10 with a panel of tissue stains (immunohistochemistry) and studied four by electron microscopy. All 10 patients were men. Seven had a history of asbestos exposure, but no fiber types or jobs were described. Nine tumors arose in the pleura and one in the peritoneum. All 10 stained strongly for pan-keratin and keratin 7. Other mesothelioma markers, such as calretinin (8 of 10) and WT1 (4 of 6), were positive more variably. No tumor tested was positive for MOC-31, CEA (not done in one case), CD15, TAG-72 or TTF-1. Electron microscopy showed many long, slender microvilli on the tumor cells. All seven patients who had extrapleural pneumonectomy had cancer in multiple lymph nodes. Six of the seven patients with follow-up died of recurrent disease, and the article's survival figures disagree with each other. The author concluded that these tumors should remain a high-grade subtype of epithelioid mesothelioma, not sarcomatoid mesothelioma, and that they behave very aggressively.

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 series: retrospective review of pathology files, with immunohistochemistry on all 10 cases and electron microscopy on 4
• Who was studied: 10 men with pleomorphic mesothelioma (9 pleural, 1 peritoneal) from the pathology files of The University of Texas MD Anderson Cancer Center, Houston; 9 were referred to the institution and 1 was sent in consultation; mean age 66.7
• Exposure: History of asbestos exposure in 7 of the 10 patients and smoking in 5; no fiber types, products, jobs or doses were reported
• Main results:
  • In all 10 cases the pleomorphic tumor cells stained strongly for pan-keratin and keratin 7
  • Keratin 5/6 was positive in 6 of the 8 cases tested
  • Calretinin was positive in 8 of 10 cases and WT1 in 4 of 6 cases tested
  • Podoplanin was positive in 5 of 7 cases tested (mesothelin in 6 of 7)
  • None of the cases tested was positive for MOC-31, CEA, CD15, TAG-72 or TTF-1; Table 3 shows CEA was not done in case 7, so CEA was negative in the 9 cases tested and the other four markers were negative in all 10
  • In all 10 cases mitotic activity was high (over 20 per 10 high-power fields)
  • In the 4 cases studied by electron microscopy, the tumor cell surfaces were covered by many long, slender microvilli
  • In all 7 extrapleural pneumonectomy specimens, multiple lymph nodes contained metastasis
  • Of the 7 patients with follow-up, 6 died of recurrent disease (results text: 3 to 7 months after diagnosis, mean 7.3 months) and 1 was alive with recurrent disease 3 months after extrapleural pneumonectomy
• The authors' conclusion: The author concluded that the immunohistochemical profile resembles other epithelioid mesotheliomas, that immunohistochemistry and electron microscopy can help diagnosis, that pleomorphic mesothelioma should remain a high-grade subtype of epithelioid (not sarcomatoid) mesothelioma, and that because it behaves very aggressively it should be mentioned in pathology reports

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleomorphic, Mesothelioma, Asbestos Exposure, Pleura, Peritoneum, Eosinophilic, Calretinin, Podoplanin (D2-40).

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