Fetal adenocarcinoma of the lung(FLAC)is a rare tumor.Due to its different clinicopathological fea-tures,biological behavior and clinical outcome,FLAC is classified into low-grade FLAC(L-FLAC)and high-grade FLAC(H-FLAC).Most patients with H-FLAC are middle-aged heavy smokers.Here,we describe an extremely rare case of a young male patient who denies smoking and initially presents with a mass on the top of the head and is eventually diagnosed with H-FLAC.The aim of this article is to improve the understanding and awareness of FLAC,and increase the attention to the disease,so as to prevent the underdiagnosis and misdiagnosis of the disease,strengthen early identification and accurate diagnosis,and pro-mote subsequent effective treatment and improve prognosis.