retroperitoneal endodermal sinus tumor

例句：

1. 1. The patient was diagnosed with a retroperitoneal endodermal sinus tumor and underwent surgery to remove it.
   患者被诊断出患有腹膜后内胚层窦状肿瘤，并接受了手术以切除它。
2. 2. The tumor was located in the retroperitoneal area, making it difficult to access for treatment.
   肿瘤位于腹膜后区域，使得治疗难以进行。
3. 3. The patient's condition worsened after the surgery, necessitating further investigation into the cause of the retroperitoneal endodermal sinus tumor.
   手术后，患者的病情恶化，需要进一步调查腹膜后内胚层窦状肿瘤的原因。