Abnormal 18F-FDG and 18F-MFBG Uptake in the Skeletal System of an Adult Patient With Neuroblastoma in the Absence of a Detectable Primary Tumor

A 30-year-old woman was evaluated for recurrent fever and pancytopenia. 18F-FDG PET/CT revealed diffuse skeletal involvement, consistent with disseminated metastatic disease. Histopathologic analysis of a bone marrow biopsy confirmed the diagnosis of neuroblastoma. The patient subsequently received neuroblastoma-targeted chemotherapy. Following treatment, she participated in a clinical trial and underwent an 18F-MFBG PET/CT examination, which demonstrated multiple skeletal metastases. Notably, neither imaging modality identified a primary tumor site. This case illustrates that metastatic neuroblastoma in adults may present with extensive osseous involvement in the absence of a detectable primary tumor, even after comprehensive functional imaging with both 18F-FDG and 18F-MFBG.