I have unexplained deep ache in up right back 2 yrs. mri spine ok. chest xray ok. mammogram ok. ultrasound rt breast ok. could this b missed tumor?

Back pains: Right upper back pain is in the territory of the right kidney. You need to address the issue with abdominal and pelvic ultrasound since you could have a stone or obstruction of the right kidney secondary to bladder obstructionby stone or gynecological tumors causing secondary obstruction to the right kidney. The retroperitoneal region could harvest a tumor or fibrosis or referred pain from lungs.

No test is 100%: accurate, but with a normal spine MRI, it would be exceedingly unlikely for your back pain to be due to a tumor. Breast cancer would not present as back pain either.