Grading of Soft Tissue Sarcomas: Review and Update

Abstract

Abstract Context.—Histologic grading is the most important prognostic factor and the best indicator of metastatic risk in adult soft tissue sarcomas. The most commonly used systems are the French grading and the National Cancer Institute grading. Both are 3-grade systems and are mainly based on histologic type and subtype, tumor necrosis, and mitotic activity. Rules for using grading should be strictly respected and limitations of grading should be known to obtain the best performance. The most controversial point is the respective values of histologic typing and grading. Histologic typing should be clearly defined before any attempt at grading, and grading should not be used on tumors of intermediate malignancy such as atypical fibroxanthoma and on some sarcomas such as dedifferentiated liposarcoma. However, grading is useful in more than 90% of adult soft tissue sarcomas and has been adapted to pediatric nonrhabdomyosarcomatous sarcomas. Current grading is not suitable for core needle biopsies. Objective.—To review the current value and limitations of histologic grading in soft tissue sarcomas. Data Sources.—The reviews on grading and original studies on prognostic factors in soft tissue sarcomas were analyzed. Conclusions.—Grading is the best predictor of metastasis outcome in adult soft tissue sarcomas and should be part of the pathologic report. Grading should be adapted to the modern management of patients and complemented by radiologic and molecular parameters.