Vimentin is a 57 kDa intermediate filament (IF) protein, which form part of the cytoskeleton of vertebrate cells. Among the Ifs, vimentin belongs to the class III, showing a high degree of specificity for cells of mesenchymal origin. The cell type specificity, displayed by each of the IF subtypes, was initially thought to be retained malignant cells as well as their normal counterpart, which made Ifs important as diagnostic markers in histogenesis. The coexpression of intermediate filaments, particularly vimentin and cytokeratin, has now been demonstrated in a variety of normal cells/tissues and in neoplastic lesions, necessitating the use of a panel of antibodies in differential tumor diagnosis.