Primary mucinous adenocarcinoma of the left renal pelvis with ectopic inferior vena cava and invasion of the left renal vein and the adjacent inferior vena cava: a case report

Primary mucinous adenocarcinoma of renal pelvis is an extremely uncommon malignant tumor without typical clinical manifestations and imaging characteristics. A definite diagnosis often depends on postoperative pathological results. Operation is the preferred choice of treatment, but prognosis is unsatisfactory. We describe a 42-year-old male patient who was admitted for repeated and intermittent pain of left abdominal flank for more than 5 years and aggravation of the symptom for more than 1 month. In the course of disease, he was misdiagnosed twice as a renal cyst in other hospitals. However, mild percussive pain was discovered in the left kidney area during this hospitalization. Moreover, abdominal computed tomography (CT) scan of our hospital demonstrated that a huge mixed-density mass derived from left kidney, along with congenital variation of the inferior vena cava and filling defect area in the left renal vein and the adjacent inferior vena cava. After adequate preoperative preparation, he was treated with radical resection of the left kidney and artificial vascular replacement of the inferior vena cava segment containing the emboli. The mass was verified to be mucinous adenocarcinoma by postoperative pathological result. In the end, he was diagnosed as primary mucinous adenocarcinoma of the left renal pelvis with ectopic inferior vena cava and invasion of the left renal vein and the adjacent inferior vena cava. Two weeks after operation, he recovered and was discharged. There was no evidence of recurrence after more than 4 years of follow-up. Blood oncogenic biomarkers were valuable in diagnosis by reviewing literature. In conclusion, Primary mucinous adenocarcinoma of the kidney is easy to be misdiagnosed as renal cyst. Preoperative CT and blood oncogenic biomarkers are extremely important for preliminary diagnosis. Postoperative pathological result is the gold standard for final diagnosis. Although prognosis is generally unfavourable, radical resection of the tumor can benefit patients.