Immunohistochemistry of soft tissue tumors: progress and prospects.

The immunohistochemical definition of soft tissue tumors has only begun (table 1). A number of antigens described here play a role in diagnostic pathology, and a few have been shown to be specific markers for certain types of cell differentiation. The detection of a wide variety of antigens in soft tissue sarcomas may initially prove confusing in some areas. For example, when specific markers are used, multidirectional differentiation in a tumor may be found more frequently than it is now, making more sarcomas actually "mesenchymomas." In such situations, certain types of differentiation may imply more or less aggressive behavior. It is also possible that panels of different immunohistochemical reagents may be required to determine a specific histogenesis. Furthermore, interpretive caution is clearly necessary, since many sarcomas contain normal tissues. Owing to the aggressive nature of sarcomas, more information on their biochemical composition will be required for proper diagnosis and clinical management. As pathologists, we are in a key position to contribute to the understanding of these tumors. In-situ biochemical analysis of sarcomas making use of immunohistochemical methodology is a powerful tool in the investigation of the difficult problems of histogenesis, tumor heterogeneity, and biologic potential.