From the Guidelines
An AML (Angiomyolipoma) on a kidney ultrasound is a benign tumor that typically appears hyperechoic and homogeneous, but its characteristics are not pathognomonic and may require further evaluation with contrast-enhanced ultrasound or other imaging modalities like CT or MRI. I would explain to a patient that this is a common finding that contains blood vessels, muscle cells, and fat tissue, which makes it relatively easy to identify on ultrasound due to its fat content 1. Most AMLs are small, cause no symptoms, and require no treatment other than occasional monitoring with follow-up ultrasounds. However, larger AMLs (typically over 4 cm) may need closer monitoring or intervention because they have a small risk of bleeding. Some key points to consider when evaluating an AML on kidney ultrasound include:
- The tumor's size and growth pattern, as larger tumors are more likely to cause problems 1
- The presence of multiple or bilateral tumors, which may indicate an underlying genetic condition like tuberous sclerosis complex 1
- The patient's overall health and medical history, as certain conditions may increase the risk of complications from an AML Treatment options for larger AMLs include embolization (blocking blood flow to the tumor) or partial nephrectomy (surgical removal of the tumor while preserving kidney function). Patients with tuberous sclerosis complex are more likely to develop multiple or larger AMLs that require closer follow-up. I would reassure the patient that most AMLs are discovered incidentally, remain stable in size, and rarely cause problems, but regular monitoring is important to ensure any growth is detected early 1.
From the FDA Drug Label
The key eligibility requirements for this trial were at least one angiomyolipoma of ≥ 3 cm in longest diameter on CT/MRI based on local radiology assessment, no immediate indication for surgery, and age ≥ 18 years.
An Angiomyolipoma (AML) on a kidney ultrasound is a type of tumor that is being studied in the context of Tuberous Sclerosis Complex (TSC). The FDA drug label does not provide a direct definition of what an AML is, but it mentions that patients in the study had at least one angiomyolipoma of ≥ 3 cm in longest diameter on CT/MRI.
From the Research
Definition and Composition of Angiomyolipoma (AML)
- Angiomyolipoma (AML) is the most common benign tumor of the kidney, composed of blood vessels, smooth muscle, and fat components in varying proportions 3, 4, 5, 6.
- AMLs are typically divided into the sporadic type and tuberous sclerosis complex (TSC)-associated type, with TSC-associated AML developing at a younger age and exhibiting a faster growth rate 3.
Classification and Characteristics of AML
- AMLs are classified as classic AML, fat-poor AML, and epithelioid AML, with epithelioid AML being rare and showing aggressive behavior leading to distant metastasis and mortality 3.
- The tumor's composition and characteristics, such as the presence of aneurysmal vessels, can increase the risk of bleeding, with larger tumors (diameter > 4 cm) being at higher risk 4.
Diagnosis and Imaging
- AMLs are often incidentally discovered on imaging, and their characteristic appearance on imaging, due to the abundant fat tissue, makes them easily diagnosable 5.
- However, some AMLs may contain too little fat, making diagnosis more challenging and increasing the difficulty in differentiating them from renal cell carcinoma (RCC) 5.
Management and Treatment
- Management of AML is based on clinical presentation and should be individualized for every patient, with treatment modalities ranging from active surveillance to more invasive approaches 3, 5.
- Treatment intervention is recommended for TSC-associated AML > 3 cm, even in asymptomatic cases, and for asymptomatic sporadic AML > 4 cm in size or with an intra-tumoral aneurysm of > 5 mm 3.