[Immunohistochemical methods in the diagnosis and differential diagnosis of mesenchymal skin tumors].

TNM classification, including staging and grading, cannot replace histogenetic classification of mesenchymal skin tumors; moreover, histogenetic classification is the basis for correct interpretation of the morphological criteria of malignancy. Histogenetic tumor classification can be improved by special methods, such as immunohistochemical studies of routinely formalin-fixed, paraffin-embedded material; such studies are especially advantageous in tumor diagnosis. Immunohistochemical methods are also useful in classifying less well differentiated mesenchymal tumors, which otherwise would be descriptively designated as round-celled, spindle-celled, pleomorphic, myxoid, epitheloid or pericytomalike sarcomas. Moreover, further knowledge can also be acquired about tumors with characteristic structure, but uncertain histogenesis. A prerequisite for optimal results is careful comparison of the morphological findings with routine (H&E) strains and immunohistochemical reactions. Thus, overinterpretation and misinterpretation can also be avoided in artefacts which, if misinterpreted, could have grave consequences.