We report the case of a 25-year-old woman with a chance detection at x-ray of a well-defined mass in the right upper lobe during a medical examination. The patient suffered from a modest flu syndrome, with cough and fever. She was a current smoker. CT scan showed a homogeneous well-defined perihilar mass without calcifications, located in the right upper lobe and fully surrounded by aerated parenchyma. A right upper lobectomy with mediastinal lymph node sampling was performed. A pathologic diagnosis of well-differentiated fetal adenocarcinoma of the lung was made and staged as T2N0. Few cases of this type of malignancy have been reported in literature.