Undifferentiated embryonal sarcoma of the liver masquerading as a cystadenoma in a young adult: a case report.

Background: Undifferentiated embryonal sarcoma of the liver is an infrequent hepatic malignancy, primarily observed in the pediatric population. This neoplasm is exceedingly rare among adults. Despite its scarcity in adult cases, it remains imperative to accurately discern undifferentiated embryonal sarcoma of the liver utilizing diverse imaging modalities to prevent misdiagnosis with more prevalent benign and malignant hepatic masses. In this case, a comprehensive imaging examination was conducted, encompassing ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography-computed tomography scans. Notably, the positron emission tomography-computed tomography scan revealed ¹⁸F-fluorodeoxyglucose uptake characteristics indicative of malignancy, providing a pivotal clue for prompt diagnosis of undifferentiated embryonal sarcoma of the liver.

Case presentation: This report presents the diagnostic procedure employed for a 37-year-old female patient of Han ethnicity in China diagnosed with undifferentiated embryonal sarcoma of the liver. The patient was admitted with a 2-day history of mid-upper quadrant abdominal pain. The patient's temperature and inflammatory markers, such as white blood cell count and hypersensitive reactive protein, were slightly elevated. Ultrasound showed a cystic-solid nodule in the liver. The computed tomography revealed a cystic mass in the right lobe of the liver, characterized by a low-density shadow and a lack of significant enhancement during contrast-enhanced scanning, initially suggesting cystadenoma. Enhanced magnetic resonance imaging revealed a block-like abnormal signal shadow in the right hepatic lobe, suggestive of various etiologies, including benign lesions, cystadenoma with hemorrhage, or hemangioma with hemorrhage. However, the positron emission tomography-computed tomography showed increased ¹⁸F-fluorodeoxyglucose consumption within both the cystic wall and lesion, raising suspicion of malignancy. Surgical resection of the posterior hepatic lobe was performed under general anesthesia after comprehensive preoperative preparations. During the procedure, a space-occupying lesion was identified in the right posterior hepatic lobe, adhering to the diaphragm. Surface liver parenchyma overlying the tumor exhibited rupture, with several blood clots visible. The tumor was successfully and completely excised. Pathological examination revealed a fusiform cell tumor, necrosis, hemorrhage, cystic changes, cellular atypia, mitotic images, and eosinophilic globules suggestive of undifferentiated embryonal sarcoma of the liver. Immunohistochemical staining indicated CK (+), vimentin (Vim; +), Desmin (+), actin (-), α1-AT (+), GPC-3 (+), PDGFRa (+), MDM2 (+), P16 (+), Ki-67 (+) 30-35%, and PAS (+). The patient underwent five cycles of combination chemotherapy with ifosfamide and epirubicin, administered at 21-day intervals at our hospital. Following 3 years of postoperative surveillance, the patient remained stable, with no evidence of hepatic tumor recurrence.

Conclusion: On the basis of this case and a comprehensive literature review, we recommend that clinicians consider the possibility of undifferentiated embryonal sarcoma of the liver in patients presenting with non-specific clinical and serological markers, particularly when there is inconsistency between ultrasound and computed tomography imaging findings, along with elevated ¹⁸F-fluorodeoxyglucose uptake observed in both the cystic wall and lesion on positron emission tomography-computed tomography examination. Given the rarity and high-grade malignancy of undifferentiated embryonal sarcoma of the liver, heightened clinical awareness and recognition are crucial for early diagnosis and successful therapy.