罕見案例報告：腎血管平滑肌脂肪瘤合併靜脈侵犯

鄭偉權，張殷綸，羅浩倫

高雄長庚紀念醫院泌尿科

Rare Cases Report: Angiomyolipoma with Aggressive Behavior of Venous Invasion

Wei-Quen Tee, Yin-Lun Chang, Hao Lun Luo

Department of Urology, Chang Gung Memorial Hospital, Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan.

Introduction
Renal angiomyolipoma (AML) is the most common type of benign kidney tumor. It is composed of fat, smooth muscle, and blood vessels. Venous invasion is a common complication of renal cell carcinoma (RCC) but is rarely occurs in AML. Despite AML benignity, it can be aggressive with a locoregional and venous invasion. We present two rare cases of renal AML with intravascular invasion.

Case presentation 1

A 65-year-old woman had a medical history of hypertension gained help at our emergency department due to right upper quadrant pain and nausea for days. Abdominal computed tomography (CT) showed gallbladder stone and thickening wall of the gallbladder, favoring cholecystitis which was compatible with her symptoms. However, accidentally noticed of left renal pelvis mass (72mm) with extension into the left renal vein and IVC, suspect liposarcoma and left renal multiple nodules up to 20mm may be due to angiomyolipoma. She had received antibiotic treatment for acute cholecystitis. We arranged CT guided biopsy for her renal mass. Pathologic showed negative for malignancy. 2 months later, we combined general surgeon (GS), cardiovascular surgeon (CVS) to perform elective operations of laparotomy left radical nephrectomy, IVC thrombectomy, and cholecystectomy. Intraoperative ultrasound was used for identified the margin of intravascular thrombus. The patient was recovered smoothly. The renal pathology report revealed angiomyolipoma with renal vein and IVC invasion.

Case presentation 2

A 48-year-old previously healthy woman was incidentally noted with a renal mass with highly suspect AML for years. She had followed up on her renal mass with abdominal CT annually. However, the tumor was progressing in size and she was transferred to our hospital. Abdominal CT showed a right renal fat-containing mass (83x93mm) with invasion of the right renal pelvis, focal protrusion to anterior perirenal space, and intravascular invasion on the right renal vein with tumor extension to intrahepatic IVC. Renal liposarcoma needed to be ruled out. We combined GS and CVS to perform laparotomy radical nephrectomy, IVC cavotomy, and thrombectomy. We arranged cardiopulmonary bypass due to intraoperative ultrasound showing IVC thrombus up to near right atrium level. The procedure smoothly without complication. The final pathology report showed angiomyolipoma.

Discussion

Renal AML are unilateral and sporadic in most cases, with a female predominance. Venous invasion of AML has not been widely studied taking into consideration its rare occurrence. It can undergo a malignant transformation if the growth of the tumor was rapid, especially in the epithelioid subtype. However, benign renal AML has been reported to show signs of invasion without pathological malignant characteristics. These 2 cases that we presented showed the aggressive behavior of benign AML.

The treatment of renal AML needs to consider tumor size, associated symptoms, and complications. The most recommended surgical treatment for tumor size was a cutoff of 4cm in diameter. Nephron-sparing nephrectomy, radical nephrectomy, and tumor embolization are the options for treatment. However, radical nephrectomy is recommended if venous invasion and suspicion of malignancy. We performed radical nephrectomy in our cases due to abdominal CT initially suspect liposarcoma and venous invasion.

Conclusion
Benign renal AML may present in aggressive behavior mimicking malignant tumors. Collaboration between cardiovascular surgeons and general surgeons can lead to a better outcome.