Congenital peribronchial myofibroblastic tumor: a case report.

We describe a rare occurrence of congenital peribronchial myofibroblastic tumor of the lung presenting in early fetal life. A female patient in the 24th week of gestation who presented with polyhydramnios was admitted for examination. Ultrasound examination revealed a mass compromising the lungs. Because the intrauterine fetal death was revealed by the ultrasound, delivery was induced. Necropsy revealed a pulmonary lesion compromising the left lower pulmonary lobe together with hepatomegaly. Microscopic analysis of the lung showed a lesion with a storiform arrangement of spindle cells with focal peribronchial distribution. Hepatic architecture was diffusely altered by fibrotic tissue. Immunohistochemical analysis on the pulmonary lesion showed high vimentin positivity in the fusocellular components, pointing to the mesenchymal nature of the lesion. Significant differentiation of smooth muscle tissue, as indicated by high HHF35 positivity, was also observed. Electron microscopy on the pulmonary lesion revealed elongated cells with some cytoplasmatic processes, a finding that is also compatible with mesenchymal differentiation.