title: Primary Retroperitoneal Myxoid Liposarcomas.
abstract: Myxoid liposarcomas (MLSs) are genetically defined by the presence of DDIT3 gene fusions and most commonly arise in the extremities of young adults. Whether MLSs develop primarily in the retroperitoneum is controversial, and a recent retrospective study found no molecularly confirmed examples. Because MLSs tend to metastasize to deep soft tissues, purported examples of primary retroperitoneal lesions might represent distant metastasis, most commonly from extremities. In addition, well-differentiated or dedifferentiated liposarcomas, which are characterized by MDM2 amplifications, may exhibit prominent myxoid changes and mimic MLSs. Here, we document 5 cases of MLSs that originated in the retroperitoneum that were identified through critical clinicopathologic reevaluation. These cases accounted for 2.3% of 214 primary retroperitoneal liposarcomas and 3.2% of 156 MLSs in our database. They occurred in 3 men and 2 women with a median age of 32 years. All tumors were localized to the retroperitoneum at presentation, and no patient developed extra-abdominal recurrences during the clinical course (median, 50 mo). All 5 cases exhibited at least focal classic histologic findings. All harbored DDIT3 gene rearrangements, and none harbored MDM2 amplifications according to fluorescence in situ hybridization. This study demonstrates that primary MLSs can occur in the retroperitoneum, albeit rarely, and can be accurately diagnosed through combined clinicopathologic and molecular analysis.
authors.affiliation: Departments of *Pathology and Clinical Laboratories †Musculoskeletal Oncology §Diagnostic Radiology ‡Rare Cancer Center, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Nokitaka
authors.initials: N
authors.lastname: Setsu
authors.forename: Mototaka
authors.initials: M
authors.lastname: Miyake
authors.forename: Susumu
authors.initials: S
authors.lastname: Wakai
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Nakatani
authors.forename: Eisuke
authors.initials: E
authors.lastname: Kobayashi
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Chuman
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Hiraoka
authors.forename: Akira
authors.initials: A
authors.lastname: Kawai
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshida
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D015321:Gene Rearrangement; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008080:Liposarcoma / Q000235:genetics / Q000473:pathology*; D018208:Liposarcoma, Myxoid / Q000235:genetics / Q000473:pathology*; D008297:Male; D012186:Retroperitoneal Neoplasms / Q000235:genetics / Q000473:pathology*; D012189:Retrospective Studies; D051742:Transcription Factor CHOP / Q000235:genetics
chemical_list: C497249:DDIT3 protein, human; D051742:Transcription Factor CHOP