Undifferentiated embryonal sarcoma of the liver

Undifferentiated embryonal sarcoma of the liver (UESL), also known as undifferentiated sarcoma of the liver or embryonal sarcoma of the liver, is a rare malignant mesenchymal tumor that primarily arises in the liver. It is the third most common primary hepatic malignancy in children, following hepatoblastoma and hepatocellular carcinoma. UESL most commonly occurs in children between the ages of 6 and 10 years, though rare cases have been reported in adults. The tumor typically presents as a large, rapidly growing mass within the liver that may appear cystic on imaging studies, which can lead to initial misdiagnosis as a benign hepatic cyst. Clinically, patients often present with abdominal pain, abdominal distension or a palpable abdominal mass, fever, and general malaise. Some patients may experience weight loss, nausea, or vomiting. In rare cases, tumor rupture can lead to acute abdominal symptoms. Laboratory findings may include elevated liver enzymes and occasionally elevated alpha-fetoprotein, though this marker is more commonly associated with hepatoblastoma. On histological examination, the tumor is characterized by a mixture of spindle-shaped and stellate cells with marked cellular pleomorphism, set within a myxoid stroma, and may contain eosinophilic globules positive for periodic acid-Schiff staining. The current treatment approach for UESL involves a multimodal strategy combining complete surgical resection with chemotherapy. Aggressive surgical resection, including hepatic lobectomy or extended hepatectomy, is considered essential for favorable outcomes. Neoadjuvant and/or adjuvant chemotherapy regimens, often based on protocols used for rhabdomyosarcoma or other pediatric sarcomas (such as combinations of vincristine, actinomycin D, cyclophosphamide, doxorubicin, ifosfamide, and etoposide), have significantly improved survival rates. Liver transplantation has been employed in cases where complete resection is not feasible. With modern combined therapy, long-term survival rates have improved substantially compared to historical outcomes, with reported survival rates exceeding 70% in recent series. However, recurrence and metastasis, particularly to the lungs, remain significant concerns requiring close follow-up.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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