IMA is an independent pathological subtype of lung adenocarcinoma, constituting approximately 5% of lung adenocarcinomas.5) It demonstrates unique pathological features characterized by proliferating mucin-secreting glandular epithelium with extracellular mucin accumulation.6) This leads to the chest computed tomography (CT) characteristics resembling inflammatory pulmonary lesions. Here, MUC5AC is linked to lung adenocarcinoma.