carcinoid tumor in appendix in 16 year old

My 16 year old daughter had her appendix removed last week.  We were told today that she had a 4.5mm malignant carcinoid tumor in her appendix that was found during pathology tests after the removal.

She has been "not well" for about a year 1/2 now.  She has been tested for all types of diseases and disorders because of fatigue, joint pain and swelling, asthma type symptoms, chest pain, digestive problems, etc.
The only thing that the drs have come up with so far is dysautonomia (an imbalance of the autonomic nervous system.)

Now, we hear about the carcinoid tumor and I read that most people that have these are in their 40s and older.  The surgeon feels comfortable with saying that the tumor was only in her appendix, and since that has been removed that we have nothing to worry about.  I do not feel so confident though.  

Could she have tumors in other parts of her body?

Could the tumor(s) make her feel ill when it was so small?

Thank you!