Human vimentin is a 53,521 dalton protein (466 amino acids) expressed in many cell types of mesodermal origin, and is one of the intermediate filament types that form the cytoskeleton. In the embryonic nervous system, however, vimentin is expressed by migrating neural crest cells forming the PNS, and by neural stem cells of the CNS. In some forms of glioblastoma, vimentin is re-expressed by the tumor cells and serves as a general indicator of their undifferentiated state. Immunohistochemical staining for Vimentin is also characteristic of sarcomas (of neural, muscle and fibroblast origin) compared to carcinomas which are generally negative. Melanomas, lymphomas and vascular tumors may all stain for Vimentin. Vimentin antibodies are thus of value in the differential diagnosis of undifferentiated neoplasms and malignant tumors.