Fig. 8
(a) A 70-year-old woman with right upper lung mass (black arrow) underwent PET/CT. A mediastinal lymph node (2R) with 0.8 cm in short diameter was showed high [18F]FDG uptake (SUVmax = 16.38), which was strongly suspected as metastasis. Whereas the uptake for this lymph node on [18F]FAPI was low (SUVmax = 2.37, green arrow). Finally, the lung mass was proven as invasive adenocarcinoma and this lymph node was proven as benign by surgical pathology. (b) A 57-year-old male was diagnosed as invasive adenocarcinoma of left lung (black arrow). The bilateral hilar (10 L,10R) and mediastinal (7, 8 L) lymph nodes showed moderate uptake on [18F]FDG PET/CT (SUVmax = 4.0-6.4). These LNs were all less than 1.0 cm (0.5–0.9 cm) in short diameter without calcification or high-attenuation. These were suspected as metastases according to the [18F]FDG PET/CT. On [18F]FAPI PET, the left hilar (10 L) and mediastinal (8 L) lymph nodes showed intensive uptake (SUVmax = 8.5–19.0, red arrows). Other lymph nodes showed low uptake of [18F]FAPI (SUVmax = 1.1–1.6, green arrows). Lymph nodes dissection confirmed that the Group10L and 8 L lymph nodes were metastases, and the Group 10R and 7 lymph nodes were confirmed benign lesions by biopsy