Li-Fraumeni syndrome is a rare disorder caused by abnormalities of the tumor-suppressor protein P53 gene. We present the case of a 26-years-old female diagnosed with bilateral ductal carcinoma. The genetic panel for breast cancer gene 1 (BRCA1) and BRCA2 mutations was negative and positive heterozygous germline tumor protein P53 gene mutations, considering Li-Fraumeni syndrome. A 2-[18F]-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) was used for postsurgical staging to show the right lung hypermetabolic nodule. A lobectomy was accomplished, and histopathology reported pulmonary adenocarcinoma. A year later, oncological follow-up was conducted with 2-[18F]-FDG PET/CT without evidence of abnormalities.