Clinical Characteristics and Outcomes of Patients with Well-Differentiated Papillary Peritoneal Mesothelial Tumors

Our plain-English summary of Clinical Characteristics and Outcomes of Patients with Well-Differentiated Papillary Peritoneal Mesothelial Tumors, by M. Offin, N. Aguirre, S.R. Yang, et al (Annals of Surgical Oncology, 2024).

The study

• Authors: M. Offin, N. Aguirre, S.R. Yang, J.L. Sauter, G. Karagkounis, M. Mohamed, A. Cercek, R. Kundra, Y. Zhang, H.M. Wang, M.P. Morris, M. Ladanyi, G.M. Nash, M.G. Zauderer
• Journal: Annals of Surgical Oncology
• Published: 2024;31(12):7973-7977
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: Well-differentiated papillary peritoneal mesothelial tumors (WDPMTs) are understudied and discrete from peritoneal mesotheliomas (PMs). We report clinicopathologic characteristics and outcomes of a large prospective WDPMT cohort.

Methods: Patients with WDPMT identified between August 2007 and December 2020 were followed through January 2023. Clinical characteristics and outcomes were annotated. Overall survival (OS) was assessed from pathologic diagnosis. Germline variants were analyzed, and targeted next-generation sequencing (NGS; MSK-IMPACT) data were compared to PMs and diffuse pleural mesotheliomas (DPMs).

Results: Among 54 patients, median age at diagnosis was 55 (range 20-76), 50% were female (n = 27), and 46% were smokers (n = 25; median 8 pack/years). Most (94%, n = 51) WDPMTs were found during surgical explorations for other indications, primarily other malignancies. Two patients underwent surgical resection for WDPMT; none received systemic therapy for WDPMT. Median OS was not reached (19/54; median follow up 4.5 years). Somatic NGS was available for 35% (19/54) of patients. TRAF7 alterations were enriched in WDPMT (89%; 17/19) compared with PM (0%; 0/50; p < 0.0001) and DPM (0%; 0/74; p < 0.0001). In WDPMT compared with PM and DPM, there were less BAP1 (0% [0/0] vs. 4% [8/50] vs. 46% [34/74]; p = 0.001 and p < 0.0001, respectively) and NF2 (0% [0/0] vs. 24% [12/50] vs. 31% [23/74]; p = 0.03 and p = 0.001 respectively) alterations. Pathogenic germline variants were present in 23% (4/17) of WDPMTs.

Conclusions: Well-differentiated papillary peritoneal mesothelial tumors were primarily incidental findings. There was no WDPMT-related mortality, so there was no distinct role for routine cytoreductive surgery or systemic therapy. Genomic profiles can help to differentiate WDPMT from DPM and PM.

© 2024. The Author(s).

In plain English

This brief report described 54 patients at Memorial Sloan Kettering Cancer Center diagnosed from August 2007 to December 2020 with well-differentiated papillary peritoneal mesothelial tumors (WDPMTs). The authors describe these abdominal growths as distinct from peritoneal mesothelioma. Asbestos exposure was not uniformly collected, and the authors said they could not comment on it. Most tumors (51 of 54) were found during surgery for other conditions, mainly other cancers. No patient received drug therapy for the tumor; two had surgery to remove it. Over a median follow-up of 4.5 years there were no deaths from WDPMT, and no tumor turned into peritoneal mesothelioma. Tumor gene testing in 19 patients found TRAF7 changes in 17. None of 50 peritoneal or 74 diffuse pleural mesotheliomas used for comparison had them, and none of the 19 had BAP1 or NF2 changes. Inherited harmful gene variants appeared in 4 of 17 patients tested. The authors concluded these tumors were mostly incidental findings, saw no distinct role for routine cytoreductive (tumor-removing) surgery or drug treatment, and said genetic profiles can help distinguish them from mesothelioma. They named selection bias as the main limitation.

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-center cohort study, described by the authors as prospective, with targeted tumor gene sequencing compared against previously published peritoneal mesothelioma data and a public diffuse pleural mesothelioma data set (brief communication)
• Who was studied: 54 patients with a pathologic diagnosis of well-differentiated papillary peritoneal mesothelial tumor seen at Memorial Sloan Kettering Cancer Center, New York, between August 2007 and December 2020, followed through January 2023. The median age was 55 (range 20 to 76) and 50% were female.
• Exposure: No asbestos exposure was studied. The authors state that asbestos exposure was not uniformly collected. The study examined clinical features, outcomes, and tumor and inherited gene changes. Smoking status was recorded: 25 patients had ever smoked, with a median of 8 pack-years.
• Main results:
  • Most diagnoses came from surgery done for other cancers (72%; 39/54) or for other benign conditions (22%; 12/54).
  • No patient required systemic (drug) therapy for WDPMT; two patients had cytoreductive surgery for WDPMT.
  • Over a median follow-up of 4.5 years (range 0.1 to 14.2), median overall survival was not reached and there were no WDPMT-specific deaths.
  • No WDPMT cases transformed into peritoneal mesothelioma during follow-up.
  • Patients with other cancers (38) compared with patients without other cancers (16) had a hazard ratio for death of 3.89 (95% CI 0.80 to 18.88, p = 0.09). This difference was not statistically significant, and median survival was not reached in either group. The authors described it as a trend toward worse survival.
  • Among the 19 WDPMT patients with tumor sequencing, 89% (17/19) had a TRAF7 alteration.
  • TRAF7 alterations were found only in WDPMT: 17/19 WDPMT, compared with 0/50 peritoneal mesotheliomas and 0/74 diffuse pleural mesotheliomas (both p less than 0.001).
  • Compared with peritoneal mesothelioma, WDPMT lacked alterations in BAP1 (0/19 vs. 30/50, p = 0.001), NF2 (0/19 vs. 12/50, p = 0.03) and SETD2 (0/19 vs. 11/50, p = 0.03).
  • Compared with diffuse pleural mesothelioma, WDPMT lacked alterations in CDKN2A/B (0/19 vs 28/74, p = 0.0005), BAP1 (0/19 vs. 34/74, p less than 0.0001) and NF2 (0/19 vs. 23/74, p = 0.001).
  • Of 17 patients who consented to germline (inherited) testing, 4 (23%) had inherited pathogenic alterations: MSH6, RAD51C, RAD51D and TGFBR1.
• The authors' conclusion: The authors concluded that WDPMTs were primarily incidental findings. Because there was no WDPMT-related mortality, they saw no distinct role for routine cytoreductive surgery or systemic therapy. They said genomic profiles can help differentiate WDPMT from diffuse pleural and peritoneal mesothelioma, and that WDPMT can likely be monitored without aggressive upfront interventions.
• Limitations the authors state:
  • The authors name selection bias as the most significant limitation, because patients were identified at a tertiary academic cancer center.
  • Most patients were diagnosed incidentally during care for other cancers, which the authors say may bias the frequency of germline alterations.
  • Asbestos exposure was not uniformly collected, so the authors could not comment on it.

Topics

Medical terms in this study, explained in our Lexicon: Well-Differentiated, Peritoneal Mesothelioma, Overall Survival, Germline Mutation, Next-Generation Sequencing (NGS), Pleural Mesothelioma, Surgical Resection, Systemic Therapy.

Related studies

• Well-differentiated papillary mesothelial tumor of the peritoneum in a young woman: A case report with molecular insights — R. Xu, S. Xu, et al. (2025)
• [Pleural Well-differentiated Papillary Mesothelial Tumor Presenting with Recurrent Pneumothorax and Pleural Effusion: A Case Report] — Z. Li, F. Kong, et al. (2026)
• Clinicopathological Characteristics of Well-differentiated Papillary Mesothelioma of The Peritoneum: A Single-institutional Experience of 12 Cases — M. Kim, H.S. Kim (2019)
• Well-differentiated papillary mesothelioma of the female peritoneum: a clinicopathologic study of 26 cases — A. Malpica, S. Sant'Ambrogio, et al. (2012)
• Combined adenomatoid tumor and well differentiated papillary mesothelioma of the omentum — Y. Hatano, Y. Hirose, et al. (2011)
• Collagenous Spherulosis in Well-Differentiated Papillary Mesothelioma in a Female With Multilocular Peritoneal Inclusion Cysts — B. AbdullGaffar, L.G. Raman (2019)

Browse more research in Annals of Surgical Oncology, or return to medical research.