'Mucin-positive' epithelial mesothelioma of the peritoneum: an unusual diagnostic pitfall

Our plain-English summary of 'Mucin-positive' epithelial mesothelioma of the peritoneum: an unusual diagnostic pitfall, by D.S. Cook, R.L. Attanoos, S.S. Jalloh, et al (Histopathology, 2000).

The study

• Authors: D.S. Cook, R.L. Attanoos, S.S. Jalloh, A.R. Gibbs
• Journal: Histopathology
• Published: 2000;37(1):33-6
• Type of article: Case report
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Aims: The histopathological, immunohistochemical and ultrastructural features of a primary 'mucin-positive' epithelial mesothelioma of the peritoneum are reported to draw attention to a potential cause of diagnostic error.

Methods And Results: Light microscopy showed an infiltrative neoplasm within the gastric wall and omentum which was composed of sheets of 'signet- ring' tumour cells and contained abundant diastase-resistant periodic acid-Schiff-positive material. Immunohistochemistry supported a mesothelial phenotype (cytokeratin AE1/3, thick membranous HBME-1, focal thrombomodulin and calretinin expression and no reactivity for carcinoembryonic antigen, Leu-M1 and Ber-EP4). Ultrastructural features showed large cells with prominent intercellular desmosomes and numerous delicate, elongated microvilli. Within intracytoplasmic neolumina, crystalloidal 'fern-like' bodies were identified with features similar to the ultrastructural appearances of hyaluronic acid crystals. Repeat histochemical analysis following hyaluronidase pretreatment revealed a significantly diminished diastase-resistant periodic acid-Schiff reaction.

Conclusions: This case of primary peritoneal 'mucin-positive' epithelial mesothelioma demonstrates morphological and histochemical mimicry with diffuse gastric adenocarcinoma. A similar case has not been previously reported in the peritoneum and an awareness of the tumour (with application of suitable ancillary studies) prevents misdiagnosis and assists in potentially difficult medicolegal cases.

In plain English

This article was a case report about one patient. A 59-year-old man had weight loss, abdominal pain and swelling, with fluid in the abdomen (ascites). An ultrasound showed a thickened stomach wall suggestive of linitis plastica or lymphoma, but stomach biopsies found no cancer. He died 3 months later. He had a 30-year history of heavy continuous asbestos exposure working as a lagger. The article did not name a fiber type. At post-mortem, tumour had replaced the omentum, mesentery and diaphragm and thickened the stomach wall. No primary tumour was found in the pleura or lung, and no hyaline plaques were seen. Under the microscope, many tumour cells had a 'signet-ring' shape and stained positive for mucin, so spread-out stomach adenocarcinoma was considered. Further antibody staining and electron microscopy fitted mesothelioma, and the final diagnosis was primary diffuse malignant mesothelioma of the peritoneum. The authors said such 'mucin-positive' mesotheliomas had been described in the pleura but not the peritoneum. They concluded that awareness of this tumour is important so that it is not mistaken for adenocarcinoma.

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 a single patient (pathology examination of post-mortem tissue). The authors stated that 'mucin-positive' mesotheliomas had previously been described in the pleura but not in the peritoneum.
• Who was studied: One 59-year-old man with weight loss, abdominal pain and abdominal distension, who died 3 months later. Hospitals in Cardiff and Milton Keynes, UK.
• Exposure: 30 years of heavy continuous asbestos exposure while employed as a lagger. No fiber type or lung fiber analysis was reported.
• Main results:
  • At post-mortem, no primary tumour was found in the pleura or lung tissue.
  • There were bilateral pleural effusions, but no hyaline plaques were seen.
  • Under light microscopy, the tumour cells in the omentum and stomach wall contained vacuoles, with many 'signet-ring cell' forms. Mucin stains were positive, and a diagnosis of disseminated diffuse gastric adenocarcinoma was considered.
  • Pretreating the tissue with hyaluronidase reduced the intensity of the acid and neutral mucin staining but did not remove it completely.
  • The mesothelial markers thrombomodulin and calretinin were focally positive.
  • The adenocarcinoma markers (carcinoembryonic antigen, Leu M1 and Ber EP4) were negative throughout.
  • Electron microscopy showed long, thin microvilli on the cells, with a length to width ratio greater than 15 to 1.
  • Electron microscopy also showed 'fern-like' crystal material inside the cells, resembling hyaluronic acid crystals.
  • The final diagnosis was primary diffuse malignant mesothelioma of the peritoneum, epithelial subtype with signet ring cell morphology.
• The authors' conclusion: The authors concluded that awareness of 'mucin-positive' mesothelioma is important, because it can mislead a pathologist into diagnosing adenocarcinoma. In this peritoneal case, the antibody staining pattern was typical of mesothelioma.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Peritoneal mesothelioma, Stomach cancer.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Peritoneum, Neoplasm, Omentum, Immunohistochemistry, HBME-1, Calretinin, Carcinoembryonic Antigen (CEA).

Related studies

• Mucin-positive epithelial mesothelioma of the peritoneum: small bowel involvement — J.H. Kim, K.Y. Kwon, et al. (2011)
• ALK positive malignant peritoneal mesothelioma mimicking inflammatory myofibroblastic tumour: a diagnostic pitfall — A. Louw, C. Wallace, et al. (2020)
• Airway epithelial NF-kappaB activation modulates asbestos-induced inflammation and mucin production in vivo — A. Haegens, T.F. Barrett, et al. (2007)
• Epithelioid and sarcomatoid malignant pleural mesothelioma in endoscopic gastric biopsies: a diagnostic pitfall — A. Agaimy, P.H. Wünsch (2006)
• Primary epithelioid haemangioendothelioma of the peritoneum: an unusual mimic of diffuse malignant mesothelioma — R.L. Attanoos, N.S. Dallimore, et al. (1997)
• Immunocytochemistry and ELISA quantitation of mucin for diagnosis of malignant pleural effusions — P.C. Yang, K.T. Luh, et al. (1992)

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