Hi Jaypo - blimey it's all worrying isn't it?
All I could find when I did a google was the following:
Avascular means: tissues that are devoid of any blood supply by arteries, veins, or capillaries.
Circumscribed means: confined to a limited area
Aetology means: the study of the causes of a disease
Now weather this is any help to you I don't know but it could be a cyst or possibly a fibroid. Do not worry about it being a 2 week referral - this will always happen if they see anything out of the ordinary & the % of it being anything sinister is very, very low.
I know it's going to worry you, I was the same in January but stay positive & try not to worry. It sounds like you're in good hands.
Love Cazi xxx