Epitrochlear nodes can be found on the inside of the upper arm, just above the elbow crease.
These are suspicious for lymphoma, melanoma, or skin infection.
Olecranon bursitis is located in a different location, near the tip of the elbow.
Regarding anatomy, you stated the lump is a couple of cm's above the elbow bone on the ulna. However, the bone above/proximal to the elbow is the humerus, whereas the bones below/distal to the elbow are the radius and ulna.
Hi, sadlamp. A cancer can do almost anything, so it comes down to a matter of what's likely versus not likely. Lymphoma can get into any bone.
"the fluid-like lump"
That doesn't seem like B-cell lymphoma at all.
"but I can still feel some residue lump"
Is it attached to the bone or is it moveable?
There is also a not-cancer condition called a ganglion cyst, which grows over tendons.
Was your immune system suppressed by the chemo? Maybe there was an infection that got into the bursa.
Good luck on your scan result, it'll probably turn out to be okay. If you didn't have the history of DLBCL, docs probably wouldn't be much concerned. But they have to check it out. It'd be nice if you can post back when you get the scan result.