Elevation of cancer antigen 15-3 owing to oncocytic renal neoplasm in a patient without evidence of breast cancer recurrence on follow-up: a case report.

Elevation of cancer antigen 15-3 owing to causes other than breast cancer recurrence can be a potential diagnostic pitfall during a patient's follow-up. It is important for clinicians to be aware of the limitations of cancer markers and to utilize a combination of diagnostic tests for patient evaluation.