Thirty-four cases of soft tissue tumors (STT) other than rhabdomyosarcoma in infants under 1 year of age were seen in our institution between 1955 and 1985. All were diagnosed initially as malignant tumors except for three cases of fibromatosis, and, thus, they received therapy appropriate at that time. During a recent pathologic review, four were seen to have had hemangioma, six hemangiopericytoma, one hamartoma, seven fibromatosis, eight fibrosarcoma, and eight unclassified sarcomas. Of these 34 cases, the initial histological diagnosis was confirmed in only 17. Sixteen patients were believed to have received inappropriately aggressive therapy; indeed, four of these cases diagnosed prior to 1975 had been benign. Major long-term side effects were seen in 7/16 treated patients (six radiotherapy, one surgery), who, in retrospect, should have received less aggressive treatment.
The reasons for these initial errors in diagnosis included doubtful histologic features associated in some cases with alarming clinical presentation. We believe that difficulties still remain in distinguishing benign from malignant STT in this age group by histological examination. Therefore, we urge extreme caution in using aggressive therapy before the diagnosis is certain.