Combined adenomatoid tumor and well differentiated papillary mesothelioma of the omentum

Our plain-English summary of Combined adenomatoid tumor and well differentiated papillary mesothelioma of the omentum, by Y. Hatano, Y. Hirose, K. Matsunaga, et al (Pathology International, 2011).

The study

• Authors: Y. Hatano, Y. Hirose, K. Matsunaga, Y. Kito, I. Yasuda, H. Moriwaki, S. Osada, K. Yoshida, A. Hara
• Journal: Pathology International
• Published: 2011;61(11):681-5
• Type of article: Case report, Review
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Herein is reported a highly rare case of combined adenomatoid tumor and well differentiated papillary mesothelioma of the omentum. A 45-year-old Japanese man was incidentally found to have a mesenteric mass during abdominal ultrasonography. Grossly, a well-circumscribed and non-encapsulated tumor, measuring 24 × 23 × 22 mm, was located in the omentum with no obvious invasion to the surrounding stomach and pancreas. Microscopically, the tumor consisted of two histological distinct components; the majority of it showed irregular arrangement of numerous cysts lined by a single layer of flattened or epithelioid cells and the multifocal minor component exhibited prominent papillary protrusions lined by a single layer of cuboidal cells with relatively uniform nucleus. Immunohistochemically, the tumor cells were diffusely positive for cytokeratin (AE1/AE3), vimentin, calretinin, D2-40 and WT-1, and negative for epithelial membrane antigen (EMA), desmin, S-100 protein and CD68. Ki-67 labeling index of the tumor cells was <5%. The postoperative course was uneventful, though he has not received any adjuvant therapy. Despite the rarity, recognition of such combined cases of mesothelial lesions is important to prevent overdiagnosis.

© 2011 The Authors. Pathology International © 2011 Japanese Society of Pathology and Blackwell Publishing Asia Pty Ltd.

In plain English

This case report from Gifu University, Japan, described a 45-year-old Japanese man with chronic hepatitis B and, according to the authors, no asbestos exposure. A routine abdominal ultrasound found the mass by chance, and CT measured it at 28 mm across. Surgeons removed a single tumor from the omentum, a fatty layer in the abdomen. There was no obvious invasion into the nearby stomach or pancreas. Under the microscope the tumor had two parts. Most of it was adenomatoid tumor, with smaller surface patches of well differentiated papillary mesothelioma. Abnormality in the cells was none to mild, no dividing cells were seen, and the Ki-67 growth marker was below 5%. Because the tumor lacked the features of malignant mesothelioma, the authors judged it a benign or indolent mesothelial tumor. The patient received no further treatment after surgery and had no clinical or radiological evidence of recurrence 3 years later. The authors found only one earlier recorded case of this combination. They concluded that such combined lesions are very rare and that recognizing them is important to prevent overdiagnosis.

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 with a brief review of the literature
• Who was studied: One 45-year-old Japanese man with chronic hepatitis B, treated at Gifu University Hospital, Japan; the mass was found incidentally on routine abdominal ultrasonography
• Exposure: The authors report that the patient had no asbestos exposure
• Main results:
  • CT showed a low-density mass 28 mm in maximal diameter; at surgery a single tumor was found in the omentum with no obvious invasion of the stomach or pancreas
  • The tumor had two components: the majority showed the pattern of adenomatoid tumor (AT), and a minor component on the tumor surface showed well differentiated papillary mesothelioma (WDPM)
  • In both components, cytological atypia was none to mild and no mitotic activity was found
  • Tumor cells of both components were diffusely positive for cytokeratin (AE1/AE3), vimentin, calretinin, D2-40 and WT-1, and negative for EMA, desmin, S-100 protein and CD68
  • The Ki-67 labeling index of the tumor cells was below 5%, with no detectable difference between the two components
  • The authors judged the lesion a benign or indolent mesothelial tumor because it lacked the histological criteria for malignant mesothelioma
  • The patient received no adjuvant therapy and had no clinical or radiological evidence of recurrence 3 years after resection
  • In the authors' literature review, only one earlier case of a composite AT and WDPM tumor had been recorded (Hanrahan, 1963)
• The authors' conclusion: The authors concluded that compound mesothelial lesions are very rare and that recognizing them is important to prevent overdiagnosis. They also stated that no treatment other than surgical excision is required in this case.

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: Adenomatoid Tumor, Well-Differentiated Papillary Mesothelioma, Omentum, Epithelioid, Calretinin, Podoplanin (D2-40), Wilms Tumor 1 (WT-1), Epithelial Membrane Antigen (EMA).

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