[Soft tissue sarcomas: the role of histology and molecular pathology for differential diagnosis]

Soft tissue sarcomas include a wide spectrum of different entities. The so-called small round blue cell tumors and spindle cell tumors are difficult to classify based solely on conventional histology. To identify different subtypes of tumors special histochemical and immunohistochemical techniques are necessary. Analysis of protein expression by immunohistochemistry provides a helpful tool to investigate the histogenesis of tumors. A basic spectrum of antibodies should be included to study these tumors: Desmin and myogenin (or MyoD1) for skeletal differentiation; S-100, NSE, CD56, and synaptophysin for neural/neuroendocrine differentiation; CD3, CD20, and CD79 alpha for malignant lymphomas; CD34, sm-actin, and beta-catenin for spindle cell tumors; additional antigens, e. g. Ki-67 and p 53, for estimation of proliferation and tumor suppressor gene malfunctions. Nevertheless, the molecular analysis of soft tissue sarcomas is necessary for demonstration of specific translocations or gene defects to specify and proof a diagnosis. For this purpose, RT-PCR for RNA expression analysis of gene fusion transcripts and multi-color FISH for analysis of chromosomal rearrangements are used. Further investigations, using DNA microrrays may help to subclassify such tumors, with respect to prognosis or prediction of therapeutic response.