Infantile myofibromatosis: the most common fibrous tumor of infancy.

We describe the clinical courses of four infants with infantile myofibromatosis (IM). This entity is a mesenchymal disorder of early infancy characterized by the formation of tumors in skin, muscle, viscera, bone, and subcutaneous tissues. Previously known as congenital generalized fibromatosis, IM was formerly thought to be a rare condition that was frequently fatal. The majority of the 170 affected patients we describe have been diagnosed since 1980. Furthermore, the mortality rate for these patients is less than 15%. Our review includes the clinical manifestations, as well as histopathologic features, and discusses the prognosis in affected infants. We found that infants with solitary lesions or multiple lesions without visceral involvement generally have a benign course. However, in patients with the multicentric form of the disorder and visceral involvement, 73% have died. Because the lesions may not be easily discernible and most spontaneously resolve, the condition is underdiagnosed and underreported. IM is the most common fibrous tumor of infancy and must be considered when evaluating children who present with either solitary or multiple tumors, particularly during the neonatal period.