Peritoneal adenomatoid (microcystic) mesothelioma

Our plain-English summary of Peritoneal adenomatoid (microcystic) mesothelioma, by D. Mori, S. Kido, M. Hiraki, et al (Pathology International, 2020).

The study

• Authors: D. Mori, S. Kido, M. Hiraki, K. Sumi, N. Ureshino, M. Masuda, K. Nabeshima, M. Akashi
• Journal: Pathology International
• Published: 2020;70(11):876-880
• Type of article: Case report
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

There are several reports of pleural adenomatoid (microcystic) mesothelioma, but peritoneal adenomatoid mesothelioma is extremely rare. A 64-year-old Japanese woman presented with no symptoms and no asbestos exposure history. An abdominal computed tomography scan revealed multiple hypervascular masses on the liver surface, pelvic cavity and anterior peritoneum. Over 10 pieces of the multiple resected tumors showed numerous microcysts composed of a bland mesothelial cell background with rich capillary vessels. Focally, atypical cells with bizarre nuclei with prominent nucleoli were observed. Adenomatoid mesothelioma was suspected based on histochemical, immunohistochemical and fluorescence in situ hybridization findings. The tumors relapsed 4 years later and metastasized to the lung, but the patient remains alive 7 years after the first tumor resection surgery. Although the prognosis of adenomatoid mesothelioma of pleural origin is poor, the progression of this peritoneal case is slow.

© 2020 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.

In plain English

This case report described a 64-year-old Japanese woman with peritoneal adenomatoid (microcystic) mesothelioma. She had no symptoms and no history of exposure to asbestos. A liver mass was found on routine ultrasound. Twelve tumors on the abdominal peritoneum, omentum and liver surface were removed by laparoscopy; the largest was 5.8 cm across. Under the microscope the tumors showed many small cysts, rich blood vessels and, in places, atypical cells. BAP1 protein was still present. A genetic test (FISH) found no homozygous p16 (CDKN2A) deletion but found hemizygous loss of NF2 in 88% of tumor cells, which the authors said strongly suggests malignant mesothelioma. New nodules appeared 6 months later. Five tumors were removed three years later during surgery for gastric cancer. Lung metastases were found at 4 years. She was alive 7 years after the first surgery while receiving chemotherapy. Based on the relapse and the spread to the lung, the authors concluded this was adenomatoid mesothelioma. They said this peritoneal tumor seemed to be slow growing.

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 64-year-old Japanese woman admitted to Saga-Ken Medical Centre Koseikan, Japan, after a liver mass was found on routine ultrasonography
• Exposure: No history of asbestos exposure was reported for the patient
• Main results:
  • At the first operation, 12 tumors in total were resected laparoscopically from the abdominal peritoneum, omentum and liver surface; the largest was 5.8 cm in diameter
  • BAP1 expression was not lost in the patient's tumor
  • FISH found no homozygous deletion of p16 (CDKN2A), but found hemizygous loss of NF2 (chromosome 22 monosomy) in 88% of the tumor cells; the Ki-67 labeling index of the first tumors was about 3%
  • The authors stated that the hemizygous loss of NF2 strongly suggests malignant mesothelioma
  • Small nodules appeared in the omentum 6 months after resection. Three years later, five adenomatoid mesothelioma tumors were resected during a distal partial gastrectomy for gastric cancer.
  • Multiple lung metastases were detected 4 years after the first surgery. Two were resected, and their Ki-67 labeling index was about 20%.
  • The patient was alive 7 years after the first surgery while receiving chemotherapy
• The authors' conclusion: The authors concluded that, based on the multiple tumors later relapsing and metastasizing to the lung, the case was adenomatoid (microcystic) mesothelioma. They also said the peritoneal tumor seemed to be slow growing despite recurrence and metastasis.
• Limitations the authors state:
  • The authors stated that the case was very difficult to distinguish under the microscope from a benign adenomatoid tumor, because most areas lacked obvious atypia
  • The authors noted there is no report examining NF2 status in a peritoneal adenomatoid tumor

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, Mesothelioma, Asbestos Exposure, Peritoneum, Mesothelial Cells, Fluorescence In Situ Hybridization (FISH), Prognosis.

Related studies

• Microcystic variant of localized malignant mesothelioma accompanying an adenomatoid tumor-like lesion — H. Umezu, K. Kuwata, et al. (2002)
• Combined adenomatoid tumor and well differentiated papillary mesothelioma of the omentum — Y. Hatano, Y. Hirose, et al. (2011)
• Synchronous occurrence of benign mesothelioma and adenomatoid tumor of uterus: A case report and review of literature — P.R. Shen, J. Cen, et al. (2019)
• Histogenesis and classification of mesonephric tumors of the female and male genital system and relationship to benign so-called adenomatoid tumors (mesotheliomas); a comparative histological study — G. Teilum (1954)
• Adenomatoid tumors of the male and female genital tract are defined by TRAF7 mutations that drive aberrant NF-kB pathway activation — B. Goode, N.M. Joseph, et al. (2018)
• Composite multicystic mesothelioma and adenomatoid tumour of the uterus: different morphological manifestations of the same process? — J.K. Chan, M.H. Fong (1996)

Browse more research in Pathology International, or return to medical research.