Malignant bile duct obstruction is a common entity in clinical practice and is infrequently caused by non-biliopancreatic neoplasms. We report the case of a male admitted with malignant obstruction of the biliary tract, showing after numerous studies that this obstruction was the initial presentation of a stage IV adenocarcinoma of the lung. Pulmonary neoplasms have variable behaviors being often spread at time of diagnosis, especially in the more aggressive subtypes. However, it is uncommon its manifestation as obstructive jaundice and when this happens it is usually due to liver damage and not to metastases to periampullary region that are extremely infrequent. In this case, the role of pathological anatomy and immunohistochemistry was essential in identifying the origin of the tumor and starting targeted treatment, since the clinical presentation and usual laboratory and image tests did not allow to differentiate it from a primary cholangiocarcinoma.