Renal angiomyolipoma is a benign tumor in your kidney. This type of tumor often doesn’t cause any symptoms. It may be discovered accidentally during testing or screening for another medical condition. Treatment usually involves active surveillance to ensure the tumor doesn’t grow or hemorrhage (bleed), which can be life-threatening.
A renal angiomyolipoma (AML) is a type of tumor in your kidney. Almost all are benign (noncancerous), but they can hemorrhage, which can be life-threatening.
A tumor occurs when cells grow and divide more than they should. A renal angiomyolipoma is made of blood vessels, muscle cells and fat.
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Angiomyolipomas are the most common kind of benign renal tumor, affecting about 0.2% to 0.6% of people, mostly women over 50.
Renal AMLs are often associated with:
Renal angiomyolipoma is caused by a genetic mutation to the TSC1 or TSC2 gene (tumor suppressor genes). They are responsible for producing tuberin, a protein that helps control cells’ growth and size. When the TSC genes mutate or change, it affects the production of tuberin, and cells may grow out of control.
Most people with renal AML don’t have any symptoms. Instead, the condition is usually discovered by accident when a person has kidney tests for another reason.
Less often, renal angiomyolipoma is discovered because of retroperitoneal hemorrhage. This occurs when part of the tumor ruptures (breaks) and blood enters the space in your abdomen (belly). Retroperitoneal bleeding is a serious, potentially life-threatening problem.
Rare symptoms include:
Renal angiomyolipomas are often diagnosed accidentally during tests to look at your kidneys for other reasons. These tumors are typically found during screening in people with tuberous sclerosis or another condition associated with AML.
A healthcare provider can diagnose a renal AML based on imaging tests that take pictures inside your abdomen:
In most cases, an imaging test is the only test needed for diagnosis. Renal angiomyolipomas are often golden yellow because of their fat content. They can range in size from 1 to 20 cm (with an average of 9 cm).
Sometimes, if your healthcare team can’t tell whether a tumor is benign or cancerous, they may order a kidney biopsy. The surgical procedure removes a small part of the tumor. Then an expert looks at the cells under a microscope to determine whether they are cancerous.
Renal angiomyolipoma treatment varies widely, from active surveillance to medication to surgical removal.
If a renal angiomyolipoma is small and isn’t causing any symptoms, your healthcare provider may recommend active surveillance. With this approach, also called “watch and wait,” you won’t have any treatment. You’ll have regular tests to monitor the tumor for any changes.
The tumor may also respond to a type of medication called mTOR inhibitors. These are a type of targeted therapy that addresses the genetic mutation. They can stop the tumor from growing or shrink it.
Your healthcare provider may recommend surgery if:
Surgical treatment may involve:
There are no strategies to prevent the genetic mutations that lead to renal angiomyolipoma.
But if you have certain other medical conditions, you should have imaging tests regularly to catch AML early:
Renal angiomyolipomas are usually small, and they rarely become a major problem. But a very small proportion can become malignant (cancerous) or cause serious bleeding. Renal AMLs should be monitored carefully. Your healthcare provider will talk to you about how often you should have imaging tests.
Even after treatment, AML can recur (come back). You should follow up with your healthcare team for regular testing.
If you’ve been diagnosed with a renal AML or one of the conditions associated with AML, be aware of the signs of retroperitoneal bleeding. Seek medical attention immediately if you experience:
A note from Cleveland Clinic
Renal angiomyolipoma (AML) is a benign (noncancerous) tumor in your kidney. It’s often found accidentally during testing or screening for another condition. If you’ve been diagnosed with a renal AML, talk to your healthcare provider about treatment options. It should be monitored regularly to prevent bleeding, which can be life-threatening.
Last reviewed by a Cleveland Clinic medical professional on 01/06/2022.
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