False positive localisation of C-11 methionine in a colloid nodule
A 45-year-old female presented with a left breast swelling since past 5 months. The swelling was single, painless, not fixed to the chest wall, and was associated with palpable left axillary lymphadeopathy. On histopathology, it was diagnosed as a case of infiltrating ductal cell carcinoma. As a part of protocol evaluating the utility of F-18 FDG and C-11 MET for prediction of response to neoadjuvant chemotherapy in locally advanced breast carcinoma the patient underwent the two studies on consecutive days. 222 MBq of FDG was injected intravenously and the patient was rested for 60 min followed by the PET/CT acquisition on a Discovery STE 16 camera (GE). 3D PET emission scan from head to thigh at 2 min per incremental bed position was acquired. C-11 MET PET/CT was done the next day 30 min after injecting 555 MBq of tracer followed by a two bed 3D PET acquisition for 10 min per bed position, with the axilla and chest in the acquisition field. Images were reconstructed using 3D VUE algorithm and viewed on a Xeleris workstation (GE) using the volumetrix protocol. On evaluation of the maximum intensity projection (MIP) image, abnormal FDG [] and MET [] accumulation was noted in the left breast and left axillary region and also in the left side of the neck. The transaxial fused PET/CT images [Figures and ] localised this uptake to a well-defined solitary hypodense nodule in the left lobe of thyroid. On retrospective examination, a nodule, soft to firm in consistency and moving with deglutition was palpable in the left lobe of thyroid. The patient was referred for a FNAC prior to starting chemotherapy, which revealed features of a simple colloid nodule. Neoadjuvant chemotherapy with cyclophosphamide, adriamycin, and 5-flurouracil was started the next day.