CEACAM5 and adenocarcinoma in situ: Pure GGNs, CEA levels ≤4.5 ng/ml, SUVmax < 2.5, tumors with a maximum diameter of ≤1 cm, or those confirmed to be adenocarcinoma in situ, minimally invasive adenocarcinoma, or invasive lepidic-predominant adenocarcinoma by frozen section may indicate segmentectomy.