NONRHABDOMYOSARCOMATOUS SOFT-TISSUE SARCOMAS OF CHILDHOOD - FORMULATION OF A SIMPLIFIED SYSTEM FOR GRADING

Because of the rarity of pediatric nonrhabdomyosarcomatous soft tissue sarcomas, it is difficult to test standardized treatment protocols fo r individual tumor entities, Grading has been used successfully to pre dict outcome of adult sarcomas, but pediatric soft tissue tumors displ ay a notable difference in clinical behavior when compared to older pa tients, To test systematically a standardized treatment strategy for p ediatric nonrhabdomyosarcomastous soft tissue sarcomas devised by the Pediatric Oncology Group, the authors devised a grading schema using c oncepts of adult grading systems and integrating the unique clinical a nd morphologic features of pediatric sarcomas, Three grading tiers wer e devised: Grade I, which includes certain pediatric tumors with littl e propensity for malignancy; Grade II, which is composed of tumors exc luded from Grades I or III by virtue of histologic diagnosis and havin g < 5 mitoses/10 high-power fields or < 15% geographic necrosis; and G rade III, which comprises certain tumors known to be clinically aggres sive by virtue of histologic diagnosis and non-Grade I tumors with > 4 mitoses/10 high-power fields or > 15% necrosis, An initial retrospect ive analysis on a series of lesions treated at a single institution in dicated a strong predictive value for grading, Subsequent prospective studies by the Pediatric Oncology Group continue to verify the prognos tic value of pediatric nonrhabdomyosarcomatous soft tissue sarcoma gra ding, and studies on individual pediatric nonrhabdomyosarcomatous soft tissue sarcomas, such as synovial sarcoma, also indicate the relative ly poor outcome of higher grade lesions, Grade can be used to predict outcome of pediatric nonrhabdomyosarcomatous soft tissue sarcomas and to devise treatment strategies for experimental protocols,