I haven't heard of it before, but sounds like a drs visit is a very good idea.
If it is Lympholcele then it can be treated, don't suffer though it , if nothing is done get second/third opinions until you get some help with this.

It seems like it will show up on imaging or ultrasound from what I read online.
Sounds like they can drain it, but they have to make sure of what it is before treating it.