[Newborn with lung mass of uncommon etiology].

Thoracic masses in neonates usually respond to congenital anomalies of the respiratory system. They comprise a large number of diseases that can compromise the development of larynx, trachea, bronchi, pulmonary parenchyma and diaphragm or chest wall. Diagnosis is carried out during prenatal period by ultrasound in most cases. In others, respiratory distress is diagnosed during post-birth examination or later as a radiological finding. We present the case of a full term newborn with prenatal diagnosis of cystic "lung mass". Physical examination was unremarkable except for decreased breath sounds on the right lung. Different image studies were carried out to characterize the lesion. The patient underwent surgery and chemotherapy at fifth month of life. Pleuropulmonary blastoma diagnosis was confirmed by pathological study of the surgical specimen. This is a rare intrathoracic malignant tumor, appearing almost exclusively in children less than 7-years-old.