Primary sternal osteomyelitis without predisposing factors is a rare condition, and it is hardly differentiated from metastatic bone tumor especially in patient with the history of primary malignancy because osteomyelities shares frequently common findings with metastatic bone lesion on $^{18}F$-FDG PET and bone scan, Although there have been several publications of primary osteomyelitis mimicking bone metastasis in the spine or extremities, we report a case of primary sternal osteomyelitis in the patient with lung cancer, which has, to our knowledge, not been reported before.