Ewing sarcoma of the liver with multilocular cystic mass formation: a case report

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. CASE PRESENTATION: 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. CONCLUSION: 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.