A 39-year-old man presented with progressive painful swelling on the left chest since 6 months. Examination revealed osseous consistency mass. CT of the thorax suggested mass arising from left fourth rib with intrathoracic and extrathoracic soft tissue components. It had extensive sunburst periosteal reaction consistent with primary malignant bone tumor. True cut biopsy revealed plasmacytoma. Routine hematological, biochemical, and bone marrow examinations were normal. Patient referred for whole-body F-FDG PET/CT to look for skeletal and bone marrow lesions. It revealed intensely metabolic left fourth rib lesion with periosteal reaction and no other lesion in the rest of the body.