Fig. 1

18F-FDG PET/CT maximum intensity projection (MIP) (A, B, C), axial 18F-FDG PET/CT fusion and CT (D, E, F) and brain T2 Flair MRI axial images (G, H, I) before treatment (A, D, G), 2 months (B, E, H) and 6 months post-treatment (C, F, I). 18F-FDG PET (MIP, A) shows giant left adrenal hypermetabolic metastatic lesion (SUVmax: 8.4, mDM: 18 × 14 × 13 cm) (red arrow) with multiple mesenteric (SUVmax: 4.6, mDM: 1.1 cm) and left iliac lymph node metastases (SUVmax: 6.3 mDM: 1.3 cm) (black arrows). In addition, a focal right gluteal muscular metastasis was seen (SUVmax: 5.1, mDM: 1.0 cm) (green arrow). Follow-up examinations after combined immunotherapy (nivolumab plus ipilimumab) (B, C and E–I) show remarkable response to treatment on 2- and 6-month images; 30% and less than 10% of adrenal lesion volume remained, respectively (SUVmax: 4.8 and 4.2, mDM: 13 × 8 × 10 cm and 7 × 9 × 4). But there is an interval decrease in size of brain metastases. Complete resolution of mesenteric and iliac lymph nodes and intramuscular gluteal lesion is also evident. 18F-FDG PET (B, C) shows increased 18F-FDG uptake on mediastinal and hilar lymph nodes suggestive of immune-mediated granulomatous reaction (blue arrows). 18F-FDG PET/CT (B, C, E, F) and brain MRI (H, I) of post-treatment (2-month and 6-month interval) reveal remarkable treatment response, even after two cycles of the treatment