So the higher resolution imagery I had on Thursday morning points to the lump being something else, most likely something that could have been safely ignored from the outset. I'm still waiting on the final radiologist report, but I had a good chat with the doctor.
What appeared to be an AVM might now be either a thrombosed AVM (basically my body did naturally what last Monday's procedure would have done) or a remnant of an infection such as TB (even if I was asymptomatic). The better quality images make a difference, but as always it's a question of interpretation based on experience and case studies.
So I might have had a procedure for nothing. I may have suffered some stress for nothing. Medical imagery isn't perfect, but it's frustrating and disappointing to have been through so much, perhaps for nothing... I should probably be feeling elated, happy, or relieved but really I think I'd rather just have a good cry about it.