A 64-year-old woman with a left upper-lung field lobulated mass.

Pulmonary mucinous cystic neoplasia (PMCN) is an uncommon primary lung malignancy. Approximately 80 cases have been reported in the literature. We describe a case and review the literature on this malignancy. Our patient was asymptomatic and presented with a left upper-lung field lobulated mass. Primary PMCN is a spectrum of mucinous cystic lesions that should be considered as a separate lung tumor entity due to its unique morphologic features and its distinct clinical behavior. Prognosis is generally better than other more common lung malignancies.