What is the recurrence rate of angiomyolipomas (AML) and how often should they be monitored?

Recurrence Rate of Angiomyolipomas

Angiomyolipomas do not truly "recur" after treatment in the traditional sense—they either grow over time if left in place, or regrow after incomplete treatment, with the highest regrowth rates occurring in patients with tuberous sclerosis complex (TSC) following embolization (42.9% of lesions over a median 78.7 months). 1

Understanding AML "Recurrence" vs. Growth

The term "recurrence" in AML literature actually refers to two distinct scenarios that require different monitoring approaches:

Growth of Existing Untreated AMLs

• Small AMLs (<4 cm) demonstrate documented growth in 27% of cases during observation periods averaging 4 years. 2
• Medium to large AMLs (>4 cm) show growth in 46% of cases over similar timeframes. 2
• Growth does not necessarily mean intervention is needed—only 1 patient with a growing tumor >10 cm required treatment despite 18 years of progression. 3

Regrowth After Embolization Treatment

• In TSC patients, 42.9% of embolized AMLs demonstrate regrowth requiring repeat intervention, with median time to regrowth of 78.7 months (range 13-132 months). 1
• Sporadic (non-TSC) AMLs show 0% recurrence after embolization in long-term follow-up. 1
• TSC patients are significantly more likely to develop recurrence than non-TSC patients (P = .01). 1

Surveillance Schedule Based on Size and TSC Status

Small AMLs (<4 cm)

• Ultrasound surveillance every 3 years is appropriate, as spontaneous hemorrhage risk is very low. 4, 5, 6
• No treatment indicated unless symptoms develop. 4, 6
• Use the same imaging modality consistently for accurate growth assessment. 4, 6

Medium AMLs (4-6 cm)

• Increase monitoring frequency to every 6-12 months using MRI or CT. 5, 6
• These lesions have the most unpredictable behavior, with 54% requiring intervention for hemorrhagic complications. 7
• Consider intervention if growth rate exceeds 0.5 cm/year. 4, 6

Large AMLs (>6 cm)

• MRI or CT surveillance every 6 months due to substantially higher bleeding risk. 5, 6
• Most will become symptomatic and should be treated electively before complications develop. 7

TSC-Associated AMLs (Any Size)

• More frequent monitoring is warranted regardless of size, as TSC-associated AMLs are larger, more frequently bilateral, and more prone to bleeding. 8, 5, 6
• Lifelong surveillance is essential after any intervention, particularly embolization, due to 42.9% regrowth rate. 1
• TSC patients present at younger ages and have tumors more likely to grow. 2

Critical Risk Factors Requiring Closer Monitoring

Beyond size and TSC status, specific features mandate intensified surveillance:

• Intratumoral aneurysms ≥5 mm dramatically increase bleeding risk and warrant prophylactic treatment consideration. 5, 6
• Growth rate >0.5 cm/year (or >5 mm/year for fat-poor lesions) indicates higher risk. 4, 5, 6
• Development of symptoms (flank pain, hematuria) requires immediate reassessment. 4, 6

Common Pitfalls to Avoid

• Do not assume embolization provides permanent cure in TSC patients—nearly half will require repeat intervention within 6-11 years. 1
• Do not discontinue surveillance after partial nephrectomy—although no recurrences were documented in one series at mean 4.7-year follow-up, longer observation may reveal late recurrences. 3
• Do not use different imaging modalities interchangeably during surveillance, as measurements vary significantly between ultrasound, CT, and MRI. 4, 6
• Rare extrarenal recurrences can occur (e.g., pancreatic AML appearing 10 years after bilateral nephrectomy in TSC). 9