From the Guidelines
Angiomyolipoma is a benign (non-cancerous) tumor of the kidney composed of blood vessels, smooth muscle cells, and fat tissue. These tumors are relatively common, affecting about 0.3-3% of the general population, and are more prevalent in women than men [ 1 ]. Most angiomyolipomas are sporadic (occurring randomly), but approximately 20% are associated with genetic conditions like tuberous sclerosis complex. The name "angiomyolipoma" describes its composition: "angio" refers to blood vessels, "myo" to muscle cells, and "lipoma" to fat tissue.
Key Characteristics and Diagnosis
Most angiomyolipomas are discovered incidentally during imaging studies performed for other reasons, as they typically don't cause symptoms when small. However, larger tumors (generally over 4 cm) may cause flank pain, blood in urine, or rarely, life-threatening bleeding if they rupture. The vessels within angiomyolipomata are fragile because they lack a complete elastic layer; microaneurysms can therefore appear on these vessels and bleed spontaneously [ 1 ]. Imaging modalities such as ultrasound, CT, and MRI can be used for diagnosis, with each having its advantages and limitations. For instance, ultrasound does not deliver radiation and has high accuracy in patients with small body habitus, but its accuracy decreases in patients with large body habitus [ 1 ].
Treatment and Management
Treatment depends on tumor size, symptoms, and risk factors. Small, asymptomatic angiomyolipomas are usually monitored with periodic imaging, while larger tumors or those causing symptoms may require intervention such as embolization (blocking blood supply to the tumor) or partial nephrectomy (surgical removal of the tumor while preserving kidney function) [ 1 ]. The risk of malignant transformation is extremely rare, which is why these tumors are classified as benign. For patients with tuberous sclerosis complex (TSC), mTORC1 inhibitors have been shown to reduce the size of angiomyolipomas and may be considered as a treatment option [ 1 ].
Considerations for Tuberous Sclerosis Complex (TSC)
In patients with TSC, angiomyolipomata tend to be multiple and bilateral, and may arise at a younger age, be more prone to bleeding complications, and grow faster than in those with sporadic angiomyolipomata [ 1 ]. The management of angiomyolipomas in TSC patients should consider the potential benefits and risks of different treatment options, including the use of mTORC1 inhibitors, and should be tailored to the individual patient's needs and circumstances.
From the Research
Definition and Composition of Angiomyolipoma
- Angiomyolipoma (AML) is a benign tumor of the kidney, composed of a mixture of three tissue components: blood vessels, smooth muscle, and adipose cells 2, 3.
- It is the most common benign tumor of the kidney 3.
Diagnosis and Treatment
- Diagnosis of AML is commonly made using ultrasound and CAT scans, although arteriograms were previously used 2.
- Treatment of AML varies from case to case, ranging from minimally invasive approaches such as selective embolization of the renal artery to invasive wedge resection, partial nephrectomy, or radical nephrectomy 4.
- Larger AMLs have a tendency to bleed and may require intervention, while smaller ones can be followed conservatively 2.
Clinical Characteristics and Complications
- AMLs are generally asymptomatic, but they can cause serious complications such as hemorrhage, which is the most common serious complication 5.
- Rarely, AML can extend into the renal vein or vena cava, and even into the heart, leading to potentially fatal complications if not managed properly 3.
- Epithelioid AML is a variant with malignant potential, and AMLs can also occur in other organs, including the anterior mediastinum 5, 6.