I have a brain cyst

I have been trying to find information about brain cysts but haven't been able to find much. I was hoping that I could get some answers here.
I'm a 20 year old female, I had a brain MRI and it showed a perfectly round 3mm brain cyst in the white matter of my right parietal lobe. How does a brain cyst form in the white matter? Most of the information I found regarding brain cysts only mentions cysts that are filled with spinal fluid (such as arachnoid cysts). My cyst isn't connected to anything (such as a ventricle) that could cause it to be filled with fluid. It's just sitting there by itself. I have never had any traumatic brain injuries or anything of that sort.
Does anyone know anything about this type of cyst?

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There are usually names for cysts by what they are in - and yours is a white matter. The brain is composed of white and gray matter.

The white matter of the brain contains nerve fibers.  If you look at the pics of an actual brain, you will see it has different colors on the edges than in the center.

However, in many MRIs, they find "white matter" which means white spots (how confusing!) and that happens from migraines to MS to other diseases, to you have to read the report carefully.

As far as I know, the development of a cyst anywhere in the body is pretty much idiopathic (of unknown origin).

If you are not having symptoms, they would tend to just watch something like that, I would think.