Clinicopathological Characteristics of Well-differentiated Papillary Mesothelioma of The Peritoneum: A Single-institutional Experience of 12 Cases

Our plain-English summary of Clinicopathological Characteristics of Well-differentiated Papillary Mesothelioma of The Peritoneum: A Single-institutional Experience of 12 Cases, by M. Kim, H.S. Kim (In Vivo, 2019).

The study

• Authors: M. Kim, H.S. Kim
• Journal: In Vivo
• Published: 2019;33(2):633-642
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background/aim: Well-differentiated papillary mesothelioma (WDPM) is histologically characterized by papillary architecture with fibrovascular cores, lined by bland mesothelial cells. We recently experienced a case of WDPM associated with multiple peritoneal inclusion cysts, which prompted us to initiate a comprehensive review of previously diagnosed WDPM cases.

Materials And Methods: The clinicopathological characteristics and immunophenotype of 12 cases of peritoneal WDPM were investigated using a review of electronic medical records, pathological examination, and immunostaining.

Results: The patients' ages ranged from 23 to 75 years. No patient had endometriosis or a previous history of asbestos exposure. Ten tumors were detected incidentally during surgery for other causes. Most tumors appeared as a small, single nodule on the peritoneal surface, but in three cases, WDPM presented as multiple lesions. All but one patient had no symptoms. All the patients examined are still well without postoperative recurrence. Histologically, all cases demonstrated typical papillary architecture with fibrovascular cores. The mesothelial cells lining the papillae consisted mostly of single row of cells, although areas of proliferation to multiple layers were observed in a few cases. Their nuclei appeared bland, but two cases exhibited mild nuclear atypia and prominent nucleoli. Immunostaining revealed that the mesothelial cells were positive for D2-40, cytokeratin 5/6, cytokeratin 7, and Wilms' tumor 1.

Conclusion: We herein demonstrated the clinicopathological characteristics of peritoneal WDPMs. WDPM has distinct pathological features. Although all cases we examined were uneventful after surgery, further surveillance is recommended since the biological behavior of WDPM is still uncertain.

Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

In plain English

This case series from one Korean hospital described 12 patients diagnosed with well-differentiated papillary mesothelioma (WDPM) of the peritoneum between January 2005 and September 2018. The authors reviewed medical records, re-examined the tissue under the microscope, and used immunostaining, which tests cells for specific proteins. Patients were aged 23 to 75 (median 64); seven were women and five men. None of the 12 had a recorded history of asbestos exposure, and none of the seven women had endometriosis. In 10 patients the tumor was found by chance during surgery for another condition. Tumors measured 0.1 to 3.0 cm; nine were single and three multiple. Only one patient had symptoms, abdominal discomfort, which the authors thought was likely caused by accompanying peritoneal inclusion cysts rather than by the WDPM itself. No tumor showed invasion of underlying tissue, and two showed mild abnormality of cell nuclei. No patient had a recurrence after surgery, although the article does not say how long most were followed. The authors concluded that the behavior of WDPM is still uncertain and recommended further surveillance of patients.

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: Single-institution retrospective case series: review of medical records, re-examination of pathology slides, and immunostaining of previously diagnosed cases
• Who was studied: 12 patients diagnosed with peritoneal well-differentiated papillary mesothelioma at a hospital in Seoul, Republic of Korea, from January 2005 to September 2018; aged 23 to 75 years (median 64); 7 women and 5 men
• Exposure: Asbestos was not the subject of the study. A history of asbestos exposure was one of the details taken from the medical records, and none of the 12 patients had one. No fiber types or doses were studied.
• Main results:
  • Ages ranged from 23 to 75 years (median 64); 7 of the 12 patients (58.3%) were women and 5 (41.7%) were men
  • None of the 12 patients had a previous history of asbestos exposure
  • None of the 7 women had evidence of peritoneal endometriosis
  • In 10 of the 12 cases (83.3%) the tumor was found incidentally during surgery for other causes
  • Tumors ranged from 0.1 to 3.0 cm. Nine (75.0%) were a single mass and three (25.0%) were multiple nodules on the peritoneal surface.
  • Only one patient had symptoms (abdominal discomfort). This was the patient whose tumor was associated with multiple peritoneal inclusion cysts.
  • The authors thought this patient's symptom was likely caused by the multiple peritoneal inclusion cysts rather than by the WDPM itself
  • No case showed invasion of the tissue beneath the mesothelium, and no mitotic figures (dividing cells) were seen
  • Two of the 12 cases (16.7%) showed a few areas of mild nuclear atypia and variation in cell size
  • Immunostaining results among the cases tested: D2-40 positive in 8 of 8, CK5/6 in 11 of 12, CK7 in 4 of 4, and calretinin in 3 of 3. WT1 was diffusely positive in 7 of 10 and focally positive in 2 of 10. PAX8 was positive in 2 of 7. EMA was focal and very weak in both cases tested. Ki-67 labeling index was less than 1% in 9 of 12 cases.
  • No patient had a postoperative recurrence. The only follow-up time given is for the representative case: no recurrence at 6 months.
• The authors' conclusion: The authors concluded that WDPM is a rare mesothelial tumor whose biological behavior is still uncertain. Although all cases were uneventful after surgery, they recommended further surveillance of patients.
• Limitations the authors state:
  • The series included only peritoneal WDPMs, not pleural or tunica vaginalis cases, so the authors said the occurrence of WDPM in men might have been underestimated
  • Not all cases were tested with every antibody
  • The authors said genetic analysis would be needed before drawing firm conclusions about PAX8 expression and how WDPM develops

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: Well-Differentiated Papillary Mesothelioma, Peritoneum, Mesothelial Cells, Asbestos Exposure, Papillae, Nuclear Atypia, Podoplanin (D2-40), Cytokeratin 5/6.

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