Angiomyolipoma

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).

Angiomyolipomas are often described as hamartomas, which means that they are focal, abnormal growth 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.

Interestingly, the tumors develop more often in the right kidney than in the 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.