[Cystic mucinous pulmonary tumor of borderline malignancy. Report of a case].

A cystic mucinous borderline tumor was discovered in a sixty two year old man, presenting as a cystic mass in the right lower lobe. A first diagnosis of bronchiolo-alveolar carcinoma was made on bronchial biopsies. Surgical specimen examination revealed a lung mucinous cystic borderline proliferation similar to ovary borderline mucinous tumors. Such an unusual localisation has been already reported. The diagnostic difficulties are reviewed.