You have had a comprehensive set of tests that would rule out many of the major diseases leading to the symptoms.
Further evaluation of the upper digestive tract can be done. Inflammation, an ulcer or GERD are all possible, and I would suggest an upper endoscopy to evaluate this.
If negative, repeating the PET scan or obtaining an MRI of the area can be considered.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
www.kevinmd.com