Diagnostic classification of soft tissue malignancies: A review and update from a surgical pathology perspective

Soft tissue sarcomas encompass a broad spectrum of histologically, clinically, and molecularly diverse neoplasms that present unique diagnostic and therapeutic challenges. Accurate classification is essential both for appropriate risk stratification and for guiding clinical management. Once classified almost exclusively based on the morphologic appearance of the tumor by light microscopy, many soft tissue sarcomas are now known to manifest recurrent patterns of genetic alterations. In addition to enabling molecular confirmation of histologic diagnoses, discovery of these recurrent genetic alterations has helped to refine existing morphologic definitions of sarcoma subtypes and even prompted the discovery of new subtypes. As therapy for sarcoma has become increasingly tailored to a specific entity, the integration of molecular data has assumed added importance in diagnostic decision making. In this article, we summarize principles of the histologic evaluation of soft tissue sarcomas, discuss specific diagnostic features of several of the most common sarcoma subtypes, and describe our vision for a future of soft tissue sarcoma diagnosis that merges morphologic, genetic, and epigenetic features to arrive at diagnoses that are aligned with tumor-specific, biologically targeted treatment approaches.