retroperitoneal tumor

例句：

1. 1.He was diagnosed with a retroperitoneal tumor and underwent surgery.
   他被诊断出患有腹膜后肿瘤，并接受了手术。
2. 2. The patient's condition worsened after the surgery, requiring further treatment.
   手术后，患者的病情恶化，需要进一步治疗。
3. 3. The tumor was located in the lower part of the abdomen, making it difficult to access.
   肿瘤位于腹部下部，难以触及。