Two men with metastatic paraganglioma/pheochromocytoma underwent PET/CT examination in our hospital to understand the treatment effect and progression of the disease. Both patients had previously been treated with 131I-MIBG, and at this evaluation, both of them underwent 68Ga-DOTATATE and 18F-MFBG PET/CT. The 68Ga-DOTATATE PET/CT showed more metastases in the images of these 2 patients. This case highlighted that 68Ga-DOTATATE PET/CT is superior to 18F-MFBG PET/CT in detecting metastases from paraganglioma and pheochromocytoma in these 2 patients.

Chemokine receptor 4 (CXCR4) is a 7-transmembrane G protein-coupled receptor, and pentixafor is considered to be a potent ligand for the CXCR4 receptor. Recently, 68 Ga-pentixafor has been reported as a potential PET imaging agent for CXCR4-positive tumors and inflammatory lesions, including adrenocortical lesions. We report a case of primary aldosteronism due to adrenocortical carcinoma with intense 68 Ga-pentixafor activity on PET/CT.

Objectives: Although FAPI, as a pan-tumor tracer, shows high expression in the malignancy imaging, FAPI uptake is also seen in some benign lesions. The purpose of this study was to retrospectively analyze the characteristics of benign lesions with FAPI uptake on 68Ga-FAPI PET/CT imaging. Methods: The electronic medical and imaging records of patients undergoing 68Ga-FAPI PET/CT PET/CT imaging in the Department of Nuclear Medicine of our hospital from March 2020 to March 2022 were retrospectively analyzed. Patients with benign lesions confirmed by histopathological analysis or long-term follow-up of FAPI-positive lesions were included in the study. Results: A total of 44 patients (i.e., 44 benign lesions) were included in this study, including 14 women and 30 men, ranging in age from 19 to 74 years. Benign lesions involved eight systems, including liver (n = 3), tail of pancreas (n = 3), stomach (n = 3), esophagus (n = 1), lung (n = 14), and mediastinum (n = 2), sinuses (n = 1), brain (n = 2), lymph nodes (n = 5), kidneys (n = 4), bones (n = 2), muscles (n = 1), thyroid (n = 1), parathyroid gland (n = 1) and breast (n = 1). The mean SUVmax (p = 0.471) and mean TBR (p = 0.830) of benign lesions in the eight systems were not significantly different. Conclusion: Our studies have shown that in addition to malignant tumors, certain benign lesions also show uptake of FAPI, and it is necessary for doctors to distinguish these benign lesions from true malignant tumors. Advances in knowledge: Benign lesions may also show FAPI expression, which may make the differential diagnosis of benign and malignant lesions difficult and should be alerted by physicians.