In cases wherein metastatic disease diagnosis in lung cancer is difficult with imaging, tissue biopsy should be performed. A 77-year-old woman presented with a complaint of cough. Positron emission tomography-computed tomography showed a left lung tumor with fluorodeoxyglucose accumulation, multiple lymphadenopathies, and right-rib sclerotic lesion. Although the diagnosis was lung adenocarcinoma, the bone lesion required differentiation from traumatic changes. A costal biopsy showed bone lesions as post-fracture healing changes, leading to variation in the therapeutic strategy to curative. In patients with lung cancer, history of trauma, and bone lesions with fluorodeoxyglucose accumulation, aggressive tissue biopsy is recommended for accurate staging.