18Fluorine-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) plays a pivotal role in the staging, restaging, and surveillance of various bone tumors, including plasmacytomas and osteosarcomas. Solitary plasmacytomas most frequently occur in the bones and are primarily treated with either surgery or radiotherapy. Radiation-induced osteosarcomas (RIOS) usually develop after a median interval of 11 years between radiation and sarcoma presentation. However, these can rarely present with a short latent period of 4 years or even lesser. In such cases, whole-body imaging plays a vital role in the early detection and management of RIOS. Herein, we present the case of a 29-year-old female patient with solitary plasmacytoma undergoing a follow-up whole-body 18F-FDG PET/CT, which revealed metastatic RIOS after a short latent period.