Repeated selective arterial embolization without surgical resection in the management of a giant sporadic renal angiomyolipoma in a female patient of childbearing age – A Case Report

Introduction: Angiomyolipomas (AML) are the commonest benign renal tumors. Most are small and found incidentally, but some can reach sizes of >20cm (giant AMLs). Due to their risk of spontaneous hemorrhage, these giant AMLs are most commonly treated by surgical resection with or without preoperative Selective Arterial Embolization (SAE). To our knowledge, there have been no giant AML cases that were treated solely by SAE in the published English literature.

labelled as a giant AML (although some have a lower cut off value of >10 cm). Giant AMLs are clinically signifi cant due to the potentially life-threatening complication of retroperitoneal hemorrhage and hence they merit early prophylactic intervention [1].
Elective Selective Arterial Embolization (SAE) is a minimally invasive treatment option observed to have outstanding technical success rates while preserving renal function and it is the treatment of choice for large or symptomatic AML. They also allow rapid hemodynamic stabilization in those patients presenting with acute spontaneous hemorrhage [2].
We present a clinical case of sporadic giant renal AML on a female patient of child bearing age measuring 25.3×19.6×9.4 cm presenting as a painless palpable abdominal mass. She responded well to four cycles of minimally invasive SAE and achieved size reduction after the third and fourth cycle to a current size of 13.6×10.3×9.3 cm.

Case presentation
We present a 32-year-old east Asian female patient with    At 80-months follow up the patient remained clinically well with no episodes of colic or hematuria and will continue to be followed up with routine CT scans.

Discussion
AMLs are the commonest benign renal tumors with a reported incidence of 0.4% and a higher predisposition in females [1]. Histology tends to show perivascular epithelioid cell tumors composed of adipose tissues, atypical blood vessels and smooth muscles. These atypical blood vessels are prone to aneurysmal formation and subsequent rupture. Renal AMLs may present sporadically or in association with tuberous sclerosis complex. These tumors tend to grow slowly, but some may enlarge up to 4 cm per year, especially during pregnancy or oral contraceptive therapy [3]. Giant AMLs are rare, with only 9 other sporadic cases reported in literature that are larger than 20 cm. To date, there is no universally agreed defi nition for giant AMLs, but a common cut off value is >20 cm [4] but others have put a lower value of >10 cm [5].
Although most non-giant AMLs are asymptomatic and discovered incidentally, all cases of giant AML identifi ed by Alshehri were symptomatic at the time of diagnosis [4].
Symptoms included dull abdominal pain, fl ank mass, abdominal bloating and nausea or vomiting. It is well known that that AMLs >4 cm have a higher incidence of spontaneous bleeding leading to retroperitoneal, renal subcapsular or perineal space hemorrhage [5,6]. Risk factors for bleeding include tumor size, grade of angiogenic component of tumor and association with tuberous sclerosis [7]. As more than 25% of AMLs carry estrogen and progesterone receptors they are thought to grow during pregnancy or with oral contraceptive use. There are now numerous case reports of spontaneous bleeding of AML during pregnancy. None of which met the criteria of a giant AML with a cut off value of >20cm [8].
Renal ultrasound is a safe diagnostic modality to identify AMLs as well-circumscribed hyperechogenic masses with posterior acoustic shadowing. Contrast enhanced CT is an accurate diagnostic modality to detect the presence of fat attenuation and differentiate from renal cell carcinoma, though diagnosis may be challenging in 5% of AMLs with minimal fat content [9]. Interventions are offered in patients with tumor diameters >4 cm or those who are symptomatic. Options include tumor enucleation, partial or total nephrectomy, or minimally invasive therapies such as selective arterial embolization, radiofrequency ablation or cryoablation [10].
Surgery is currently advocated for hilar tumors, those with uncertain diagnosis or have vascular anatomy which might cause technical failure during embolization [11]. Embolization with alcohol/Lipiodol mixtures or particles such as polyvinyl alcohol (PVA) or spheres is preferred as they allow complete occlusion of the feeding arteries [10].
At present, the only medical therapy for AMLs is the use of the mammalian target of rapamycin (mTOR) inhibitor called Everolimus. However, its use has only been reported in patients with tuberous sclerosis associated AMLs [12].
There have been case reports of giant AML treated with SAE pre-operatively to reduce operative blood loss.
Singla, et al. reported a case of giant renal AML measuring 26×22 cm that was treated with preoperative embolization followed by partial nephrectomy [13]. To our knowledge, our case is the fi rst known reported of giant renal AML to be managed with SAE alone.
Multiple studies have quantifi ed the success and complication rates of SAE, albeit only in smaller AMLs. In a systematic review of 524 AMLs, Murray, et al. observed a technical success rate of 93% for SAR, with mean tumor size reduction from 8.8 to 3.4 cm (38%) at 39 months [14]. Repeat embolization or surgery was required in 21% of patients, usually due to tumor growth or revascularization. Post-embolization syndrome was the commonest complication with an incidence of 35.9%. No procedural mortality was reported.
Hocquelet, et al. found a mean volumetric reduction of 72% at median follow-up time of 28 months in 39 AMLs [15]. Tumor size reduction has been found to be greatest early after embolization before gradually plateauing and has been better in tumors with larger angiomyomatous components or lower fat components [16,17].
We, the authors, feels that with increasing worldwide use of CT scans the discoveries of such giant AMLs may become more common. Discoveries in younger, asymptomatic female patients (like in our case) will add further challenge to an already complex clinical scenario. Due to their rarity, the optimal management of giant AMLs has not been established. As interventional radiology expertise continuous to grow, we currently do not know what is the role of SAE as a sole treatment modality in the management of giant sporadic AMLs and will require further long-term data based on randomized studies.

Conclusion
We report a case of sporadic giant renal AML on a female patient of child bearing age that underwent four SAE sessions with good response. The patient declined further surgical resection and remains well after 80 months follow up. Repeat SAE is a safe treatment modality and may be a viable nonsurgical option in the management of giant AMLs.