Well-Differentiated Papillary Mesothelioma with Omental Calcifications: A Case Report and Review of the Literature

Our plain-English summary of Well-Differentiated Papillary Mesothelioma with Omental Calcifications: A Case Report and Review of the Literature, by A.S. Erem, S.S. Allamaneni, T.S. Braverman (The American Journal of Case Reports, 2020).

The study

• Authors: A.S. Erem, S.S. Allamaneni, T.S. Braverman
• Journal: The American Journal of Case Reports
• Published: 2020;21:e920487
• Type of article: Case report
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

BACKGROUND Omental calcifications of the peritoneum are typically small and asymptomatic. However, larger psammomatous bodies that cause symptoms such as abdominal pain and bloating are often associated with tumors such as primary serous papillary carcinoma, mesothelioma, or metastatic ovarian cancer. CASE REPORT We describe omental calcifications in a 68-year-old woman who had been asymptomatic for the last 10 years. The case details the histomorphologic features and immunohistochemical signature of a 4.0×3.5×1.0 cm mass consisting of mature adipose tissue that was surgically removed together with an 8.5×6.5×1.8 cm irregular intra-abdominal/mesenteric mass composed of yellow-red fatty tissue. Microscopic sections contained fat with variable clustered classic/psammomatous calcifications, some with a thin epithelioid periphery, in association with a very focal and subtle papillary surface epithelial/mesothelial proliferation. Tumor cell invasion was not observed during examination. Immunohistochemical staining showed that mesothelial cells in the mass were strongly positive for calretinin and focally positive for EMA, CK903, and vimentin. Strong nuclear positivity for PAX8 was also reported. Additional stains were added in response to this pattern, showing strong positivity for CK8, moderate positivity for BAP1, focal positivity for ER, minimal positivity for CD56, and negativity for CK5/6 and D2-40. Three possible explanations are suggested for the phenomenon observed in the pathology slides: reactive mesothelial hyperplasia, well-differentiated papillary mesothelioma, or serous papillary carcinoma of the peritoneum. CONCLUSIONS Findings suggest that these calcifications are a benign, reactive phenomenon, and that the abundance of psammoma bodies may be related to ongoing crops of papillary mesothelial hyperplasia or benign well-differentiated papillary mesothelioma.

In plain English

This was a case report with a review of published reports on well-differentiated papillary mesothelioma (WDPM), a rare tumor. A 68-year-old woman with a 10-year history of calcium deposits (calcifications) in the omentum, a fatty layer in the abdomen, developed recurrent abdominal pain. The article does not report any asbestos exposure for her. Surgeons removed a 4.0×3.5×1.0 cm fatty abdominal-wall mass, compatible with a lipoma, and an 8.5×6.5×1.8 cm intra-abdominal/mesenteric fatty mass containing clustered psammomatous calcifications and a very focal papillary cell proliferation. No tumor cell invasion was seen. Staining was mixed: calretinin favored WDPM, while ER, minimal CD56 and absent D2-40 and CK5/6 pointed toward serous papillary carcinoma. An expert opinion favored benign WDPM, and she reported complete symptom relief at 5 months. The authors suggested the calcifications were a benign, reactive phenomenon related to papillary mesothelial hyperplasia and/or benign WDPM, noting the findings did not rule out other diagnoses. Citing other studies, they noted WDPM is not commonly associated with asbestos exposure.

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 of one patient, combined with a literature review of published WDPM case reports and case series (1990 to 2019) used to compare staining patterns
• Who was studied: One 68-year-old woman with a 10-year history of omental calcifications and recurrent diffuse abdominal pain, who had elective abdominal surgery in January 2019; the authors are from Saba University School of Medicine and The Jewish Hospital – Mercy Health, Cincinnati
• Exposure: No asbestos or other occupational exposure is reported for the patient. The discussion, citing other studies (references 5 and 38), states that unlike mesothelioma, WDPM is not commonly associated with asbestos exposure.
• Main results:
  • A 4.0×3.5×1.0 cm mass of mature adipose tissue in the abdominal wall was compatible with an encapsulated lipoma
  • An 8.5×6.5×1.8 cm irregular intra-abdominal/mesenteric mass of yellow-red fatty tissue was excised; it contained clustered classic/psammomatous calcifications with a very focal and subtle papillary surface epithelial/mesothelial proliferation
  • Mesothelial cells in the mass were strongly positive for calretinin, focally positive for EMA, CK903 and vimentin, and showed strong nuclear positivity for PAX8
  • Additional stains showed strong positivity for CK8, moderate positivity for BAP1, focal positivity for ER, minimal positivity for CD56, and negativity for CK5/6 and D2-40
  • The authors interpreted calretinin positivity as much more likely in WDPM, but the lack of D2-40 or CK5/6 (along with ER positivity and minimal CD56) as pointing toward serous papillary carcinoma
  • No tumor cell invasion was observed, which the authors said supported a benign diagnosis
  • An expert consultant's opinion favored benign pathology (WDPM)
  • The patient reported complete relief of her symptoms at her 5-month follow-up
• The authors' conclusion: The authors suggested that the calcifications are a benign, reactive phenomenon and that the abundance of psammoma bodies may be related to ongoing crops of papillary mesothelial hyperplasia and/or benign well-differentiated papillary mesothelioma.
• Limitations the authors state:
  • The authors state that the staining and the characteristics of the calcifications did not rule out other possible diagnoses
  • The authors state that even with expert review, the microscopic and staining appearance may not allow these conditions to be told apart
  • The pathology was described as inconclusive, which led to a referral for an expert opinion

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, Serous Papillary Carcinoma, Mesothelioma, Ovarian Cancer, Epithelioid, Immunohistochemistry, Mesothelial Cells.

Related studies

• Combined adenomatoid tumor and well differentiated papillary mesothelioma of the omentum — Y. Hatano, Y. Hirose, et al. (2011)
• Fine-needle aspiration of a well-differentiated papillary mesothelioma in the inguinal hernia sac: A case report and review of literature — Y.Y. Wheeler, F. Burroughs, et al. (2009)
• Well-differentiated papillary mesothelioma of the peritoneum: a pathological analysis and review of the literature — A.V. Hoekstra, M.W. Riben, et al. (2005)
• 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)
• Well-differentiated papillary mesothelioma of the female peritoneum: a clinicopathologic study of 26 cases — A. Malpica, S. Sant'Ambrogio, et al. (2012)
• Well-differentiated papillary mesothelioma with invasive foci — A. Churg, T. Allen, et al. (2014)

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