60-y-old woman with recurrent HER2-positive breast cancer in medial left mastectomy site after left simple mastectomy and prophylactic right mastectomy. (A and B) Baseline 18F-FDG PET (A) and fused 18F-FDG PET/CT (B). (C and D) After 2 cycles of exemestane and trastuzumab treatment, slight increase in tumor metabolic activity, with SUV of 12.7 compared with SUV of 11.1 at baseline, was seen on 18F-FDG PET (C) and fused 18F-FDG PET/CT (D). In addition, a few mildly hypermetabolic left hilar lymph nodes, which suggested metastases (not histologically proven), showed decrease in metabolic activity after start of treatment. Because there was no response to treatment in recurrence at medial left mastectomy site, carboplatin treatment was initiated.