Angiomyolipoma is a rare benign kidney tumor that occurs in isolation. More rarely, it is associated with tuberous sclerosis of Bourneville. Although benign, surgery may be offered to avoid complications.

Definition

Angiomyolipoma is a kidney tumor made up of fat, blood vessels, and muscle. There are two types:

• THEsporadic angiomyolipoma, also called isolated angiomyolipoma, is the most common form. This tumor is often unique and present on only one of the two kidneys.
• THEangiomyolipoma associated with tuberous sclerosis is the less common type. Tuberous sclerosis is a genetic disorder that causes non-cancerous tumors to form in many organs.

Although non-cancerous, the risks of bleeding or spreading exist. They are all the more important if the tumor measures more than 4cm in diameter.

Diagnostic

An abdominal ultrasound allows the diagnosis to be made on the basis of:

• a small tumor
• the presence of fat in the tumor

If in doubt about the nature of the tumor, surgical exploration and biopsy will confirm the benign nature of the tumor.

The people involved and the risk factors 

Women are more at risk than men of developing angiomyolipoma when it is isolated.

People with tuberous sclerosis are more likely to have angiomyolipoma. Tuberous sclerosis often induces the formation of more than one tumor, their presence in both kidneys and larger in size. This genetic disease affects both men and women, and angiomyolipomas develop earlier than in their isolated form.

Non-cancerous tumors cause few symptoms.

Large tumors or those that bleed can cause:

• pain in the side, back, or abdomen
• a lump in the abdomen
• blood in the urine

Although benign, the angiomyolipoma tumor can be removed with surgery to prevent: 

• bleeding from the tumor
• enlargement of the tumor
• expansion of the tumor to a nearby organ

To prevent the tumor from growing, bleeding, or spreading to nearby organs, it is recommended that you follow up with the doctor at least once every two years when the tumor is no more than 4cm in diameter. The evolution will then be monitored to avoid complications.

Beyond 4cm in diameter or in the presence of several tumors, it is recommended to make a monitoring appointment every 6 months.