Immunohistochemistry in the differential diagnosis of soft tissue tumors.

Immunohistochemical reagents have allowed us to analyze each and every soft tissue lesion over the past decade. What has been learned has been extraordinarily valuable and the fact that these reagents exist has undoubtedly led to more accurate diagnoses on the whole. We have learned to speak of "differentiation" rather than "histogenesis." We have also learned that, as each marker has been held up to the test of time, there are very few perfect markers. Interpretation must always be made with (1) full knowledge of the phenotypic range of each marker, (2) knowledge of the range of marker reactivity of each tumor or lesion, and (3) the all-important clinico-morphologic setting, which must continue to weigh heavily in the diagnostic process.