IntroductionInvasive mucinous adenocarcinoma (IMA) is a special subtype of adenocarcinoma according to World Health Organization classification. IMA accounts for an estimated 2–10% of all lung cancers [1, 2]. Overall, 60–90% of IMA cases present with solitary nodules, mass shadows, or ground-glass opacity lesions, but there are also cases of extensive extension with multiple nodules or diffuse alveolar shadows. Therefore, it is sometimes necessary to distinguish the lesions from benign pulmonary diseases such as pulmonary tuberculosis, sarcoidosis, lipoid pneumonia, and alveolar proteinosis [3, 4]. In addition, it is often detected at an advanced stage, which makes it difficult to treat surgically; however, limited reports of such cases have been described [2]. Here we describe a case of IMA that was detected preoperatively as an infiltrative shadow over the entire right lower lung lobe and treated with surgical resection along with a review of the literature.