Diagnostic and therapeutic challenges in extragonadal yolk sac tumor with hepatoid differentiation: A case report.

Yolk sac tumors (YSTs) are rare aggressive tumors, arising most commonly in the gonads and occurring mainly in young adults. We herein report a case of an extragonadal YST with hepatoid differentiation localized in the brain and lung. A 41-year old man presented to our hospital with a generalized seizure. A head computed tomography and magnetic resonance imaging examination revealed a large mass in the left occipital lobe with associated edema. Following complete resection, the histopathological examination revealed that the mass was a highly malignant epithelial tumor with a hepatoid pattern. The serum lactate dehydrogenase and α-fetoprotein levels were elevated. Additional diagnostic imaging revealed a lesion in the upper lobe of the right lung, but no other tumor manifestations. Based on the clinical and immunohistochemical characteristics, hepatocellular carcinoma and hepatoid adenocarcinoma were excluded and the diagnosis of extragonadal hepatoid YST was established. A multimodal therapeutic approach (high-dose chemotherapy with autologous stem cell transplantation, radiation and surgery) was applied; however, the patient succumbed to refractory disease 10 months after the diagnosis. Therefore, the diagnosis and treatment of hepatoid YST is an interdisciplinary challenge.