Congenital solitary fibromatosis of soft tissues, a variant of congenital generalized fibromatosis. 2 cases reports.

A report of 2 cases of solitary fibromatosis in a 10-day-old boy and a girl 3 years and 10 months old is presented. Both lesions were deep-seated and showed a nodular and infiltrating growth, predominantly buil-up by immature fibroblast-like cells and including hemangiopericytoma-like areas. One of the lesions also showed leiomyoma-like areas. An ultrastructural study however, revealed no intra-cytoplasmatic myofilaments. At follow-up examinations after 21 years and 1 year, respectively, there were no signs of recurrences or metastases. These 2 cases are considered to represent a solitary form of congenital generalized fibromatosis. The differential diagnosis from infantile hemangiopericytoma and fibrous lesions seen in infancy and early childhood, such as infantile fibrosarcoma, diffuse infantile fibromatosis, extra-abdominal desmoid, fibrous hamartoma of infancy and juvenile aponeurotic fibroma, is discussed.