Pediatric Fibroblastic and Myofibroblastic Tumors

Spectrum of Fibroblastic and Myofibroblastic Tumors When one considers soft tissue tumors in pediatrics, tumors of vascular (29%), neurogenic (15%), and myogenic (striated muscle, 14%) origin occur more often than fibroblastic-myofibroblastic tumors (12%). The spectrum of fibroblastic/myofibroblastic tumors is quite divergent from both clinical and histopathologic viewpoints (Table 1). These tumors are most commonly benign, but may follow an aggressive course that mimics a malignant process. The only “true” pediatric fibroblastic malignancy is infantile fibrosarcoma that has a characteristic tumor-defining translocation in most cases. Other fibroblastic/myofibroblastic tumors may be associated with congenital syndromes (inclusion body fibromatosis and fibrous hamartoma of infancy) and a predisposition to adenomatous polyps and colon cancer (Gardner-associated fibromas and desmoids). The major problem for the surgical pathologist is the similarity between myofibromas and infantile fibrosarcomas and the vast difference in treatment of myofibromas versus infantile fibrosarcoma. This presentation will be limited to infantile fibrosarcoma, myofibroma/myofibromatosis, a newly recognized entity pericytic tumor with t(7;12), inclusion body fibromatosis, fibrous hamartoma of infancy, and juvenile hyaline fibromatosis.