Oral localizations of extra-oral primary lesions metastases are extremely rare and account for only 1 to 3% of all malignant tumors of the oral cavity. A 60-year-old patient was referred to the oral surgery department by his dentist due to delayed healing of an alveolar socket following extractions performed six months earlier. The patient reported a 40-pack-year smoking history. Clinical examination revealed a fixed right submandibular lymphadenopathy and a raw, bleeding gingival lesion in the maxilla. Diagnostic investigations, including CBCT, MRI, pan-endoscopy, cerebral CT, PET scan, and histopathological analysis, were conducted. These analyses identified infiltrative lesions in the right maxillary bone with extensions, leading to a diagnosis of stage IV pulmonary adenocarcinoma with bone metastases. Multiple secondary lesions were also detected. This case highlights the importance of early detection of malignant lesions, particularly in patients with significant risk factors such as smoking or poor oral hygiene.