How do they find endo in other parts of body if endo isn’t seen on imaging?

I strongly believe I may have endo in areas of my body that a routine endo excision surgery wouldn’t look at… so when I see all of these videos online being like, “did you know they’ve found endo in the brain, eyes, lungs, legs, etc?!” I’m like… cool… cool… but how? On cadavers?? Because in the same video, and also in my own personal experience, endo isn’t seen on imaging most of the time… so unless they’re going to do exploratory surgery on my eyes or my brain or any out-of-the-box area I suspect it may be what am I supposed to do????

Tldr: how do they find endo in the, “weird,” areas like eyes, brain, legs, lungs, etc. if endo isn’t easily seen on imaging? Is it only in cadavers? Do they just cut people open here and there and have a look around?