27 y/o M "Upper left quadrant" patient

I posted first order and second order on this patient on the forum around a week ago, today at his third visit the transient axillary lump was there and I was able to palpate it. My number one thought was.. this is adhesion of the brachial cords. The lump palpates like a non-compressible very small mass that is not moveable. It did not palpate with smooth or rounded boarders like a cyst might, but a ganglion cyst is my second ddx based on his history of trauma to that area. My question for you all is this: Could adhesion appear to come and go? Could some of his activities provoke the “lump” to come and go? Thanks for your continued input!