Selected topics in peritoneal pathology

Our plain-English summary of Selected topics in peritoneal pathology, by P.M. Baker, P.B. Clement, R.H. Young (International Journal of Gynecological Pathology, 2014).

The study

• Authors: P.M. Baker, P.B. Clement, R.H. Young
• Journal: International Journal of Gynecological Pathology
• Published: 2014;33(4):393-401
• Type of article: Review
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This essay considers selected peritoneal lesions many of which were the subject of studies coauthored by Dr Robert E. Scully. His article on multilocular peritoneal inclusion cysts has largely led to these lesions being considered non-neoplastic, eschewing the term cystic mesothelioma. These cysts are often associated with reactive mural mesothelial proliferations that can potentially lead to a misdiagnosis of mesothelioma. Clinical findings, such as a common association with endometriosis or prior operations, can prompt consideration of a reactive lesion. Mesothelial hyperplasia may be difficult to distinguish, when florid, from mesothelioma but a variety of gross and microscopic features will aid their recognition. Nodular peritoneal aggregates of histiocytes (sometimes admixed with mesothelial cells) may occasionally be a striking finding that can be misdiagnosed as a metastasis if the patient has a known neoplasm. Appreciation of their bland nuclear features and histiocytic nature, confirmed by immunohistochemical markers, facilitate the diagnosis. Various forms of peritonitis are briefly considered including sclerosing peritonitis, a process sometimes associated with luteinized thecomas (thecomatosis) of the ovaries, an entity first appreciated by Dr Scully. Mesotheliomas are briefly reviewed emphasizing the caution that should be used in applying the designation "well-differentiated papillary mesothelioma." Many interpret the latter as benign, but multifocal lesions must be thoroughly examined histologically because of potential overlapping features with malignant mesothelioma. The morphologic spectrum of malignant mesothelioma and its usually straightforward distinction from müllerian neoplasms is considered, as is its occasional presentation as a dominant ovarian mass. The spectrum of low-grade serous peritoneal neoplasms including the "psammocarcinoma" is reviewed. Finally, various benign müllerian lesions, particularly endometriosis and endosalpingiosis, may be conspicuous in peritoneal specimens and sometimes are grossly striking. The usual presence of benign endometrioid epithelium and stroma should facilitate the correct diagnosis of endometriosis, but in cases in which the stroma is atrophic or the sole component (stromal endometriosis), diagnostic problems may arise.

In plain English

This article was a review essay by three pathologists, written to honor Dr Robert E. Scully. It did not study a new group of patients. It described how pathologists can tell apart lesions of the peritoneum (the lining of the abdomen), many found in gynecologic specimens. The topics included multilocular peritoneal inclusion cysts, which the authors described as reactive rather than a form of cystic mesothelioma. They also covered mesothelial hyperplasia, histiocytic aggregates, peritonitis, serous tumors and endometriosis. The authors listed features that favor malignant mesothelioma over hyperplasia, such as invasion, necrosis and marked nuclear atypia. They stated that peritoneal malignant mesotheliomas are much less common than pleural ones. They also recalled their own earlier study of 75 peritoneal malignant mesotheliomas in women, in which biphasic and pure sarcomatoid tumors made up 5 of the 75 cases. The authors wrote that the label well-differentiated papillary mesothelioma should be used sparingly and only for thoroughly sampled, solitary tumors. The article did not mention asbestos or any cause of mesothelioma. The foreign materials it named, such as starch and talc from surgical gloves and fibers from sponges and drapes, were described as causes of granulomatous peritonitis.

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: Narrative review (essay in a symposium honoring Dr Robert E. Scully), focused mainly on peritoneal lesions studied in papers he coauthored
• Who was studied: No patient group was studied for this article; it reviews published work on tumor-like and neoplastic lesions of the peritoneum, many seen in gynecologic specimens
• Main results:
  • The review described multilocular peritoneal inclusion cysts as reactive lesions. It based this on earlier work in which a history of abdominal operation, pelvic inflammatory disease and/or endometriosis was found in most cases. This view is opposed to classifying them as well-differentiated cystic mesotheliomas.
  • The review listed features that favor malignant mesothelioma over mesothelial hyperplasia: grossly visible nodules or plaques, destructive invasion into underlying tissues, necrosis, moderate to severe nuclear atypia, and conspicuous mitotic activity.
  • The review listed noninfectious causes of granulomatous peritonitis. These included foreign material such as starch and talc particles on surgical gloves and fibers from sponges and surgical drapes. They were not discussed as causes of mesothelioma.
  • The authors stated that peritoneal malignant mesotheliomas are much less common than pleural mesotheliomas, accounting for only 10% to 20% of all mesotheliomas.
  • The authors cited their own earlier study (published 2005) of 75 peritoneal malignant mesotheliomas in women. In that study, biphasic and pure sarcomatoid tumors accounted for 5 of the 75 cases.
  • In peritoneal malignant mesotheliomas, psammoma bodies and necrosis are present in 20% to 30% of cases, according to the review.
  • The review stated that prominent ovarian involvement by peritoneal malignant mesothelioma can mimic a primary ovarian tumor.
  • The authors wrote that the diagnosis of well-differentiated papillary mesothelioma should be used sparingly, and only when the tumor is solitary and has been thoroughly sampled. This is because malignant mesotheliomas can focally contain low-grade areas that resemble it.
• The authors' conclusion: The authors concluded that peritoneal malignant mesotheliomas can be distinguished from serous neoplasms in most cases on routinely stained slides. They also concluded that the term well-differentiated papillary mesothelioma should be reserved for thoroughly sampled, solitary, non-invasive tumors.

Topics

Medical terms in this study, explained in our Lexicon: Pathology, Mesothelioma, Misdiagnosis, Reactive Mesothelial Hyperplasia, Mesothelial Cells, Metastasis, Neoplasm, Well-Differentiated Papillary Mesothelioma.

Related studies

• Benign multicystic mesothelioma and peritoneal inclusion cysts: are they the same clinical and histopathological entities? A systematic review to find an evidence-based management — A.M.C. Rapisarda, A. Cianci, et al. (2018)
• Peritoneal mesothelial hyperplasia associated with gynaecological disease: a potential diagnostic pitfall that is commonly associated with endometriosis — R. Oparka, W.G. McCluggage, et al. (2011)
• Malignant peritoneal mesothelioma in patients with endometriosis — K.J. Butnor, J. Rueckert, et al. (2018)
• Multicystic mesothelioma caused by endometriosis: 2 case reports and review of the literature — Y. Kurisu, M. Tsuji, et al. (2011)
• Multimodality imaging of common and uncommon peritoneal diseases: a review for radiologists — R.A. Vicens, M. Patnana, et al. (2015)
• Loose mesothelial cysts in the peritoneal cavity — Y. Ramirez, J. Rosai, et al. (2010)

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