Angiomyolipoma

A benign tumor of the kidney

Myoid cells with clear cytoplasm spinning off of large vessels in a background of mature fat, the classic microscopic features of angiomyolipoma

Angiomyolipome der Niere CT

CT scan of a renal angiomyolipoma.

An angiomyolipoma is a benign tumor that is most commonly found in the kidney. It is composed of blood vessels, smooth muscle, and adipose tissue. Although angiomyolipomas are generally benign, they can sometimes lead to complications, particularly if they grow large or if they are associated with certain genetic conditions.

Pathophysiology

Angiomyolipomas are classified as hamartomas, which are benign, tumor-like malformations made up of an abnormal mixture of cells and tissues normally found in the area of the body where the growth occurs. The tumor is composed of three types of tissue: thick-walled blood vessels, smooth muscle cells, and fat cells. The presence of these components gives the tumor its name: "angio" refers to blood vessels, "myo" to muscle, and "lipoma" to fat.

Epidemiology

Angiomyolipomas are relatively rare, with an estimated prevalence of 0.3% to 3% in the general population. They are more common in women than in men and are often discovered incidentally during imaging studies for other conditions. Angiomyolipomas are also associated with tuberous sclerosis complex (TSC), a genetic disorder that causes non-malignant tumors to form in many different organs.

Clinical Presentation

Most angiomyolipomas are asymptomatic and are found incidentally during imaging studies such as ultrasound, CT scan, or MRI. However, larger tumors can cause symptoms such as flank pain, hematuria (blood in the urine), or even life-threatening retroperitoneal hemorrhage if they rupture. In patients with tuberous sclerosis, multiple angiomyolipomas may be present, and they may grow larger and cause more significant symptoms.

Diagnosis

The diagnosis of angiomyolipoma is typically made through imaging studies. On ultrasound, angiomyolipomas appear as echogenic (bright) lesions due to their high fat content. CT scans can confirm the presence of fat within the tumor, which is a key diagnostic feature. MRI can also be used to characterize the lesion and assess its composition.

Management

The management of angiomyolipoma depends on the size of the tumor and the presence of symptoms. Small, asymptomatic tumors may be monitored with periodic imaging studies. Larger tumors, or those causing symptoms, may require intervention. Options include embolization to reduce blood supply to the tumor, surgical resection, or nephron-sparing surgery. In some cases, mTOR inhibitors such as everolimus may be used, particularly in patients with tuberous sclerosis.

Prognosis

The prognosis for patients with angiomyolipoma is generally excellent, especially for those with small, asymptomatic tumors. However, larger tumors or those associated with tuberous sclerosis may require ongoing management to prevent complications.

Related pages

• Kidney tumor
• Tuberous sclerosis complex
• Benign tumor
• Nephrology

External links

Classification	ICD-10: D30.0 MeSH: D018207 DiseasesDB: 29496
External resources