Fetal hydrops associated with congenital pulmonary myofibroblastic tumor

We report on a fetus with a congenital pulmonary myofibroblastic tumor, the prenatal detection of which with imaging modalities has not been reported up until now. A 32‐year‐old woman was referred to our hospital at 29 weeks’ gestation because of severe fetal hydrops. Sonograms and magnetic resonance imaging showed a large solid tumor in the left thorax. The fetus died in utero the next day. Autopsy confirmed that the tumor was confined to the lower lobe of the left lung, and circulatory insufficiency from compression by the tumor was considered to be the cause of fetal hydrops and demise. Histologic examination revealed that the tumor was composed of uniform short spindle cells with no atypia and a large number of vessels. In addition, with immunohistochemical studies, the tumor cells were stained for calponin but not for cluster differentiation (CD)‐31, CD‐34, α‐smooth muscle actin or S‐100.