Mesenchymal Markers (Nonhematopoietic)

Vimentin is one of the types of intermediate (10 nm) filaments that characterize cell types. It is a 57 kD protein and is expressed primarily in cells of mesenchymal origin. Immunogold labeling localized vimentin to the cytoplasmic processes of fibroblasts, Langerhans cells and melanocytes, with lesser amounts in the per-nuclear cytoplasm (1). Anti-vimentin antibodies were among the first antibodies available for diagnostic use. Early studies suggested that vimentin expression was relatively specific and that its detection in cells would enable diagnosticians to categorize a tumor as being of mesenchymal origin (2,3). Almost immediately thereafter, it was discovered that vimentin could be detected in cells that were nonmesenchymal. Normal and malignant melanocytes (of neuroectodermal origin) were found to strongly express vimentin (4–6). Within several years, the list of neoplasms known to express vimentin had grown significantly, and thus, its diagnostic specificity became less impressive (7).