Anti-vimentin identifies a 57-kDa intermediate filament that was first extracted from cultures of mouse fibroblasts. It often acts as a valuable control to verify that the tissue has been accurately preserved and treated. When combined with keratin, vimentin expression aids in differentiating melanomas from undifferentiated carcinomas and large cell lymphomas. All cases of melanomas and schwannomas show a strong positive reaction to vimentin. It tags various mesenchymal cell types, including melanocytes, lymphocytes, endothelial cells, and fibroblasts. In gynecological tumors, uterine endometrioid adenocarcinomas show a significantly distinct immunophenotype, characterized by the coexpression of low molecular weight cytokeratin and vimentin.