On ct scan)" 4mm hypoechoic lesion -tail of pancreas-follow-up 1 yr. with mri" how bad is this?

Lesion pancreas: The lesion you describe does suggest a cyst these do occur in pancreas kidney and liver. Pancreas malignancy is a very bad responder as a general rule as well as fast growing tumor. I would prefer surgical consultation and sooner follow up. There are oncologist surgeons who have dedicated a large part of there lives to this cancer including dr. Cameron at johns hopkins.