Angiomyolipoma

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Introduction0:00–0:26

Angiomyolipomas are the most common benign tumors found in the kidneys, although they can be found in other tissues like the liver and on rare occasions in some reproductive structures.
If we break down the word we see that they are tumors that are comprised of blood vessels (angio), smooth muscle (myo), and adipose or fat tissue (lipo).

Pathophysiology0:26–1:15

Angiomyolipomas are often described as hamartomas, which means that they are focal, abnormal growths of cells which are normally found at that site, but are disorganized.
It’s a bit like a house with a front door that can’t be reached, it’s the right part for the structure, but it’s not organized in the right way.
Angiomyolipomas also belong to the perivascular epithelioid cell tumor family, or PEComa family, meaning that they are made of epithelial-like cells that are found around blood vessels.
Now, it’s worth mentioning that normally there are no perivascular epithelioid cells that exist; the name just refers to the way that the tumor cells look under the microscope.
The actual cell type from which PEComas, including angiomyolipomas arise, is not known. The majority of angiomyolipomas will pop up sporadically - which means they are not a part of a syndrome - as isolated lesions.

Causes1:15–2:22

Interestingly, the tumors develop more often in the right kidney than the in left. However, these tumors are also strongly associated with tuberous sclerosis which is a genetic disease that causes benign tumors to develop in various parts of the body.
Individuals with tuberous sclerosis often have multiple angiomyolipomas along the surface of both kidneys, and they can be larger in size than the sporadic ones.
Regardless of whether the angiomyolipoma occurs sporadically or as a consequence of tuberous sclerosis, there is usually an underlying mutation in one of the tuberous sclerosis genes - TSC1 or TSC2 - which code for the tuberous sclerosis complex proteins hamartin and tuberin, respectively.
These proteins are part of a protein complex that acts as a tumor suppressor by inhibiting protein synthesis, which is why mutations in the complex promote uncontrolled cellular growth and proliferation.

Complications2:22–3:06

If they are small angiomyolipomas are usually harmless and don’t require treatment, but if the angiomyolipoma is large, it may start to have a mass effect pushing on healthy tissue of the kidney and impairing its function, ultimately leading to chronic kidney disease.
In rare instances this could eventually lead to end-stage renal disease and the need for dialysis. These large tumors can also develop irregular blood vessels that can steadily dilate and form an aneurysm that could rupture.
A ruptured aneurysm would cause sudden flank pain, and would have the dangerous potential of causing hypovolemic shock, especially if the angiomyolipoma involves a major blood vessel, like the renal artery.

Treatment3:06–3:46

Because these angiomyolipomas often have a high density of blood vessels they can be difficult to surgically resect. An alternative treatment which can help to preserve healthy kidney function is to destroy the blood supply of large angiomyolipomas using a procedure called embolization.
By destroying the disorganized blood vessels that help to supply the other disorganized tissue in the angiomyolipoma, it can become necrotic which shrinks the lesion and reduces the risk of hemorrhage.
Embolization can cause significant inflammation which causes "postembolization syndrome,” which is characterized by symptoms like fever, flank pain, and malaise for a few days after the procedure.

Review3:46–4:11

OK, quick recap. Angiomyolipomas are benign tumors that are comprised of a disorganized mix of blood vessels, smooth muscle, and adipose tissue.
These tumors most commonly arise in the kidneys and are strongly associated with tuberous sclerosis.