Understanding PET Scan Results After Breast Cancer Treatment: What Do the Findings Mean?

Question
My sister  was diagnosed with triple negative breast cancer 1.5cm lump. She had a lumpectomy, 4 rounds of AC and 12 weekly doses of Taxol which she finished up in April of this year. She recently went for a PET Scan and two 6mm nodes were identified. One behind the pectoral muscle (exactly where the oringal cancer was) and one axillary node. There was no hypermetabolism. Do you think this is metastatic breast cancer or could it be something else. They want to do a repeat PET in 6 months. Obviously we are very concerned. Is it possible to have a recurrence so soon after chemo has finished. Thanks for your help.

Answer
It is possible but not probable (though this may be an example of why I think postsurgical radiation therapy ALWAYS should be given after a lumpectomy). To be sure I think - since it is known where these 2 nodes are - ultrasound scanning should be used in order to try to find them again and then use ultrasound guidance to do needle biopsies of them. That way we would KNOW what they are and she would be relieved of this anxious waiting.