thank you all for taking the time to respond
unanimity was: it is a *ganglion cyst,* nobody ever saw a vascular
malformation inside ACL
I did an CE MRangiography, and indeed, the structure inside LIA did not
enhance internally, only the linining, which is consistent with a ganglion
cyst.
The serpigionous part enhances – but not like a vessel (because on
angiographic phases is not seen). It is probable just the internal lining
enhancement (so small caliper of the structure) which is a bit late.
Thank you again!