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CUAJ – CUA Best Practice Report Guo et al
BPL: AML management

Canadian Urological Association Best Practice Report: Diagnosis and management of sporadic
angiomyolipomas

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Yanbo Guo, MD ; Anil Kapoor, MD, FRCSC ; Paul Cheon, MD ; Alan I. So, MD, FRCSC ; Jean-
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Baptiste Lattouf, MD, FRCSC ; Munir Jamal, MD, FRCSC 4
1 Division of Urology, Department of Surgery, McMaster University, Hamilton, ON, Canada; Department of Urologic
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Sciences, University of British Columbia, Vancouver, BC, Canada; Departments of Surgery and Urology, Centre Hospitalier
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de l'Université de Montréal, Montreal, QC, Canada; Division of Urology, Department of Surgery, Trillium Health Partners,
Mississauga, ON, Canada

Cite as: Guo Y, Kapoor A, Cheon P, et al. Canadian Urological Association Best Practice Report:
Diagnosis and management of sporadic angiomyolipomas. Can Urol Assoc J 2020 September 8; Epub
ahead of print. http://dx.doi.org/10.5489/cuaj.6942

Published online September 8, 2020

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Introduction
Angiomyolipomas (AML) are benign neoplasms composed of varying amounts of blood vessels, smooth
muscle and adipose tissue. While being the most frequently occurring benign solid renal tumour, their
incidence in the general population is still uncommon, occurring with a frequency of 13 to 30 per
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100000. With the increased use of intra-abdominal sonography and cross-sectional imaging, more have
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been incidentally identified.
The majority of these tumours are asymptomatic, but some present with symptoms including
flank pain, hematuria, and rarely, life-threatening hemorrhage. The frequency of these presentations has
been controversial and a point of contention in their management. In an influential case series and
literature review of 253 patients, Oesterling et al. reported that 64% were symptomatic, and 40%
presented with hemorrhage. These numbers became more dramatic in tumours larger than 4cms, with
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82% being symptomatic and 51% presenting with hemorrhage. This landmark review greatly
influenced the 4cm cut off has been ingrained into urologic literature and the historically high rate of
intervention in lesions larger than 4cm. 4
In contrast, contemporary series have reported much more modest rates of 10% being
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symptomatic and only 2% risk of hemorrhage. The lack of prospective randomized studies in the
management of AMLs and the significant heterogeneity in the available retrospective evidence presents
a conundrum in clinical management.
While the majority of AMLs are sporadic, up to 20% are associated with hereditary conditions
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such as tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM). Management of
these lesions tends to differ from sporadic AMLs as they tend to present with multiple tumours and seem