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Agaimy A, Brcic L, Briski LM, Hung YP, Michal M, Michal M, Nielsen GP, Stoehr R, Rosenberg AE. NR4A3 fusions characterize a distinctive peritoneal mesothelial neoplasm of uncertain biological potential with pure adenomatoid/microcystic morphology. Genes Chromosomes Cancer 2023; 62:256-266. [PMID: 36524687 DOI: 10.1002/gcc.23118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 11/30/2022] [Accepted: 12/11/2022] [Indexed: 12/23/2022] Open
Abstract
A focal adenomatoid-microcystic pattern is not uncommon in peritoneal mesothelioma, but tumors composed almost exclusively of this pattern are distinctly rare and have not been well characterized. A small subset of mesotheliomas (mostly in children and young adults) are characterized by gene fusions including EWSR1/FUS::ATF1, EWSR1::YY1, and NTRK and ALK rearrangements, and often have epithelioid morphology. Herein, we describe five peritoneal mesothelial neoplasms (identified via molecular screening of seven histologically similar tumors) that are pure adenomatoid/microcystic in morphology and unified by the presence of an NR4A3 fusion. Patients were three males and two females aged 31-70 years (median, 40 years). Three presented with multifocal/diffuse and two with a localized disease. The size of the individual lesions ranged from 1.5 to 8 cm (median, 4.7). The unifocal lesions originated in the small bowel mesentery and the mesosigmoid. Treatment included surgery, either alone (three) or combined with hyperthermic intraperitoneal chemotherapy (two), and neoadjuvant or adjuvant chemotherapy (one case each). At the last follow-up (6-13 months), all five patients were alive and disease-free. All tumors were morphologically similar, characterized by extensive sieve-like microcystic growth with bland-looking flattened cells lining variably sized microcystic spaces and lacked a conventional epithelioid or sarcomatoid component. Immunohistochemistry confirmed mesothelial differentiation, but most cases showed limited expression of D2-40 and calretinin. Targeted RNA sequencing revealed an NR4A3 fusion (fusion partners were EWSR1 in three cases and CITED2 and NIPBL in one case each). The nosology and behavior of this morphomolecularly defined novel peritoneal mesothelial neoplasm of uncertain biological potential and its distinction from adenomatoid variants of conventional mesothelioma merit further delineation as more cases become recognized.
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Affiliation(s)
- Abbas Agaimy
- Institute of Pathology, Friedrich Alexander University Erlangen-Nürnberg, University Hospital, Erlangen, Germany
| | - Luka Brcic
- Diagnostic and Research Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Laurence M Briski
- Department of Pathology and Laboratory Medicine, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Yin P Hung
- Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Michael Michal
- Department of Pathology, Charles University, Faculty of Medicine in Plzen, Pilsen, Czech Republic
| | - Michal Michal
- Department of Pathology, Charles University, Faculty of Medicine in Plzen, Pilsen, Czech Republic
| | - G Petur Nielsen
- Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Robert Stoehr
- Institute of Pathology, Friedrich Alexander University Erlangen-Nürnberg, University Hospital, Erlangen, Germany
| | - Andrew E Rosenberg
- Department of Pathology and Laboratory Medicine, University of Miami Miller School of Medicine, Miami, Florida, USA
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