Definition: Infantile myofibromatosis is a mesenchymal disorder of infancy characterized by the formation of tumors in skin, subcutaneous tissue, muscle, bone and viscera.

Prevalence: Until now 175 cases of Infantile Myofibromatosis have been published in the English literature. The incidence of soft tissue tumors in newborns has been estimated to be 1 in 150,000 live births.

Etiology: Unknown. An association to excess estrogen production has been proposed.

Diagnosis: The diagnosis relies on identification of solid tumor masses of variable size at different locations, which are well circumscribed and sometimes well encapsulated.

Longitudinal scan of the fetal spine. Notice a large tumor mass distorting the spine (arrow). The confirmed sonographic diagnosis was myofibromatosis.

Transverse scan of the fetal abdomen. Notice the tumor mass (arrow).

MRI picture of the fetus at 30 weeks of pregnancy. Note the tumor mass (arrow).

Prognosis: The prognosis depends on the presence of visceral involvement. Of the 175 collected cases in the literature, 27 (15.5%) died. All deaths were associated with visceral involvement.