First, de Quervain's syndrome (named for Dr. Fritz de Quervain - Swiss), is not related to any shoulder problems (even though they involve tendons). Second, I am thinking you might have Shoulder Impingement Syndrome. You can Google it to see if that fits your personal symptoms. I wouldn't be too concerned about the 2 X 2mm intrasubstance tear, however, it could be a problem later if it increases (surgery). Best of wishes, jd1963!
I forgot to mention that I'm a 27 year old female. I also have de Quervain's in that wrist. I don't know if since it's a tendon issue, they could be related?