Fibroblastic-myofibroblastic tumors in children and adolescents: a clinicopathologic study of 108 examples in 103 patients.

A review of over 900 soft tissue tumors in children and adolescents revealed 108 fibroblastic-myofibroblastic tumors in 103 patients from newborn to 20 years of age, which had been accessioned in a 25-year period. Based on clinicopathologic criteria, 82 (76%) were regarded as benign, 14 (13%) as borderline, and 12 (11%) as malignant. The average age at diagnosis for the entire series was 7 years with a male/female ratio of 1.8:1. The most frequent topographic site was the extremities (48, 44%), followed by the trunk (31, 29%) and the head and neck region (27, 25%). Virtually 50% (51 tumors) of cases were diagnosed during the first year of life, and 73 (71%) occurred in the first decade. The known recurrence rate was 16% (17 cases). Fibromatosis of various subtypes accounted for 95% of the histologically benign group. Infantile myofibromatosis was the most frequent form of fibromatosis, followed by aggressive (desmoid) fibromatosis (20 cases, 19%). Ninety percent of infantile myofibromatoses were diagnosed in the first year of life. In contrast, 70% of aggressive fibromatoses occurred in the second decade. Associated conditions included familial desmoid fibromatosis, Gardner syndrome, and previous surgery. The borderline category was represented by the 14 (13% of the series) congenital-infantile fibrosarcomas. All of the 14 (13%) malignant tumors were classic adult-type fibrosarcomas that occurred only in later childhood and adolescence. Fibromatosis colli, fibrous hamartoma of infancy, juvenile nasopharyngeal angiofibroma, Dupuytren-type fibromatosis, infantile digital fibromatosis, juvenile aponeurotic fibroma, unclassified fibromatoses, and fibroma of tendon or nerve sheath constituted the remaining cases.