A morphologic variant of lung adenocarcinoma characterized by the presence of mucin pools containing islands of well differentiated adenocarcinoma cells. The disease is lung colloid adenocarcinoma (Monarch Disease Ontology id MONDO_0027772). Also known as: lung mucinous cystadenocarcinoma, lung mucinous cystic tumor of borderline malignancy, lung mucinous cystic tumour of borderline malignancy.