Congenital occurrence of solitary infantile myofibromatosis of the spleen.

Infantile myofibromatosis (IM) is a rare soft tissue tumor of infancy and childhood. We report the case of a newborn girl with an abdominal tumor discovered at 32 weeks of gestation by fetal ultrasound. She underwent a laparotomy for an unexplained abdominal mass 20 days after birth. The tumor originated from the spleen and was removed by splenectomy. There were no other abnormal findings on diagnostic modalities. Based on the histological examinations, the tumor was diagnosed as an IM. Although extremely rare during the neonatal period, solitary type IM should be considered as a differential diagnosis of the splenic tumor.