title: Ewing sarcoma of the liver with multilocular cystic mass formation: a case report.
abstract: BACKGROUND
  Ewing sarcoma is a rare tumor that occurs commonly in the long bones of children or adolescents that can also arise in soft tissues including the extremities, retroperitoneum, chest wall, and rarely in the liver as primary sites. We report a case of Ewing sarcoma arising primarily in the liver and, to our knowledge, this is the fourth reported case of Ewing sarcoma occurring in the liver.
  
  
  METHODS
  A 27-year-old Japanese woman was admitted with sudden onset right upper abdominal pain. Clinical examination revealed a multilocular cystic mass consisting of thickened, irregular septa and nodal walls in the right hepatic lobe. Ultrasound-guided aspiration biopsy of the liver mass showed clusters of small atypical round cells and the clinical preoperative diagnosis was mucinous cystadenoma of the liver. The patient underwent an extended right hepatectomy and histopathological findings revealed sheet-like proliferation of small- to medium-sized round cells. Tumor cells were positive for periodic acid-Schiff reaction and immunoreactive for glycoprotein C99 and gene NKX2.2, as well as the neuroendocrine markers, CD56 and synaptophysin. EWS-FLI-1 fusion transcript type 1 was detected by reverse transcriptase polymerase chain reaction. Pathological and molecular analysis confirmed the diagnosis of Ewing sarcoma arising primarily in the liver and the patient received adjuvant systemic chemotherapy with vincristine, doxorubicin, and cyclophosphamide, alternating with ifosfamide and etoposide. We found no evidence of recurrence 15 months after completing chemotherapy.
  
  
  CONCLUSIONS
  We present an extremely rare case of Ewing sarcoma arising primarily in the liver. To our knowledge, this is the fourth reported case of Ewing sarcoma occurring in the liver, and the first case with a multilocular cystic liver mass. Imaging examinations of the other three reported cases showed solid tumors and a diffuse enlarged liver without mass lesion. Clinicians should consider the possibility of Ewing sarcoma in young patients with a multilocular cystic mass with thick and/or irregular cyst walls in the liver.
authors.affiliation: Department of Medical Oncology, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo, 105-8470, Japan. 1755ozaki@gmail.com.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Ozaki
authors.affiliation: Department of Medical Oncology, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo, 105-8470, Japan. yujmiura@mac.com.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Miura
authors.affiliation: Department of Medical Oncology, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo, 105-8470, Japan. shigehiro_koganemaru@yahoo.co.jp.
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Koganemaru
authors.affiliation: Department of Medical Oncology, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo, 105-8470, Japan. kou_susan@yahoo.co.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Suyama
authors.affiliation: Department of Pathology, Toranomon Hospital, Tokyo, Japan. inonao3939@gmail.com.
authors.forename: Naoko
authors.initials: N
authors.lastname: Inoshita
authors.affiliation: Department of Pathology, Toranomon Hospital, Tokyo, Japan. tkshfj@gmail.com.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fujii
authors.affiliation: Department of Digestive Surgery, Toranomon Hospital, Tokyo, Japan. masaji.hashimoto@gmail.com.
authors.forename: Masaji
authors.initials: M
authors.lastname: Hashimoto
authors.affiliation: Department of Gastrointestinal Medicine, Toranomon Hospital, Tokyo, Japan. tetsu-t@toranomon.gr.jp.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Tamura
authors.affiliation: Department of Gastrointestinal Medicine, Toranomon Hospital, Tokyo, Japan. ktakeuchi@toranomon.gr.jp.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Takeuchi
authors.affiliation: Department of Medical Oncology, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo, 105-8470, Japan. takano@toranomon.gr.jp.
authors.forename: Toshimi
authors.initials: T
authors.lastname: Takano
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000378:metabolism; D005260:Female; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins / Q000096:biosynthesis; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000473:pathology*; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion / Q000096:biosynthesis; D051789:Proto-Oncogene Protein c-fli-1 / Q000096:biosynthesis; D034802:RNA-Binding Protein EWS / Q000096:biosynthesis; D012512:Sarcoma, Ewing / Q000175:diagnosis / Q000188:drug therapy / Q000473:pathology*; D014157:Transcription Factors / Q000096:biosynthesis; D029961:Zebrafish Proteins
chemical_list: D014408:Biomarkers, Tumor; C106031:EWS-FLI fusion protein; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins; C000715631:NKX2-2 protein, human; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; D014157:Transcription Factors; D029961:Zebrafish Proteins; C000715630:nkx2.2b protein, zebrafish