CEACAM5 and lung adenocarcinoma: Since type II pneumocytes are considered as the stem cells or progenitors in alveoli (32), SARS-CoV-2 infection-induced massive alveolar epithelial cell death may lead to abnormal regeneration of type II pneumocytes for repair along with the production of CEA, which was similar to the uncontrolled proliferation of lung adenocarcinoma.