Benign multicystic peritoneal mesothelioma presenting as a retroperitoneal pelvic mass in a young woman: a case report

Our plain-English summary of Benign multicystic peritoneal mesothelioma presenting as a retroperitoneal pelvic mass in a young woman: a case report, by E.A. Amaireh, O. Al-Natour, M.A. Nour, et al (Journal of Surgical Case Reports, 2026).

The study

• Authors: E.A. Amaireh, O. Al-Natour, M.A. Nour, I.A. Mahfouz
• Journal: Journal of Surgical Case Reports
• Published: 2026;2026(8):rjag710
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Benign multicystic peritoneal mesothelioma is a rare mesothelial neoplasm with fewer than 200 reported cases, typically arising on peritoneal or pelvic surfaces in premenopausal women. We describe a 21-year-old woman with a 2-week history of left lower abdominal pain. Magnetic resonance imaging showed a multiloculated cystic retroperitoneal mass adherent to the sigmoid colon, with normal ovaries and uterus. CA-125 was mildly elevated. At laparotomy, the mass was confirmed to be retroperitoneal without ovarian involvement, requiring en-bloc excision with sigmoid colectomy and primary anastomosis. Histopathology showed flat-to-cuboidal mesothelial cells with a hobnailing pattern in fibromyxoid stroma; immunohistochemistry was positive for calretinin and WT-1, and negative for SALL4, GATA3, and CD31, confirming benign multicystic peritoneal mesothelioma. At 6-month follow-up she remained asymptomatic with no recurrence on imaging. This case highlights BMPM as a mimicker of primary retroperitoneal neoplasms and the potential need for bowel resection to achieve complete excision.

© The Author(s) 2026. Published by Oxford University Press and JSCR Publishing Ltd.

In plain English

This case report described a 21-year-old woman with two weeks of worsening pain in the left lower abdomen. Magnetic resonance imaging showed a multi-chambered cystic mass in the left pelvis measuring 6.3 × 10.7 × 10 cm. It appeared to arise from the retroperitoneum (the space behind the abdominal lining) and was stuck to the sigmoid colon. Her uterus and ovaries were normal. The blood marker CA-125 was mildly raised at 83.4 U/ml. Surgeons removed the mass together with a segment of the sigmoid colon, and she went home five days later. Microscope and staining tests confirmed benign multicystic peritoneal mesothelioma (BMPM): the tissue was positive for calretinin and WT-1 and negative for SALL4, GATA3 and CD31. Malignant mesothelioma was ruled out, partly because she had no asbestos history. Citing earlier literature, the authors stated that BMPM, unlike malignant mesothelioma, has no association with asbestos exposure. At 6-month follow-up she had no symptoms and no recurrence on pelvic MRI. The authors concluded that BMPM should be considered for such masses in young women with normal ovaries.

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
• Who was studied: One 21-year-old previously healthy woman with 2 weeks of left lower abdominal pain. The authors are based at hospitals and a university in Jordan. Dates of care are not given.
• Exposure: No asbestos exposure was studied. In the discussion, citing earlier literature, the authors stated that BMPM, unlike malignant mesothelioma, has no association with asbestos exposure.
• Main results:
  • In this patient, MRI showed a multiloculated cystic lesion in the left hemipelvis measuring 6.3 × 10.7 × 10 cm. It appeared retroperitoneal in origin and was adherent to the sigmoid colon.
  • The patient's CA-125 was 83.4 U/ml, described as mildly elevated (normal below 35 U/ml). The other tumour markers were interpreted as nonspecific.
  • At laparotomy, a 10 × 8 cm retroperitoneal mass adherent to the lateral wall of the sigmoid colon was found. It was removed en bloc with a segment of sigmoid colon.
  • The patient's recovery was uneventful and she was discharged on postoperative day five.
  • Immunohistochemistry was positive for calretinin and WT-1 and weakly positive for inhibin. It was negative for SALL4, GATA3 and CD31, which the authors said confirmed BMPM.
  • Malignant mesothelioma was excluded by the absence of cytological atypia, invasion, and asbestos history.
  • At 6-month follow-up the patient was asymptomatic, with no recurrence on pelvic MRI.
• The authors' conclusion: The authors concluded that BMPM should be considered in the differential diagnosis of any multiloculated retroperitoneal cystic mass in a young woman with normal ovaries.

Topics

Medical terms in this study, explained in our Lexicon: Peritoneal Mesothelioma, Neoplasm, CA-125, Laparotomy, Histopathology, Mesothelial Cells, Immunohistochemistry, Calretinin.

Related studies

• Multicystic benign mesothelioma of the pelvic peritoneum presenting as acute abdominal pain in a young woman — J.H. Hong, S. Jeon, et al. (2013)
• Multicystic benign cystic mesothelioma presenting as a pelvic mass — M. Momeni, E. Pereira, et al. (2014)
• Benign multicystic peritoneal mesothelioma presenting as a ghost abdominal mass — H. Jerraya, W. Ghariani, et al. (2016)
• Benign Multicystic Peritoneal Mesothelioma Presenting as a Colonic Mass — K. Pierre, N.F. Gomez, et al. (2021)
• The first case of benign multicystic mesothelioma presenting as a splenic mass — A. D'Antonio, C. Baldi, et al. (2016)
• Retroperitoneal approach for recurrent benign multicystic peritoneal mesothelioma — G.D. Bakhshi, K.R. Wankhede, et al. (2013)

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