Nestin is a class VI intermediate filament (IF) protein. It has been reported that nestin expression is significantly increased in melanoma and correlated with more advanced stages of the disease. An immunohistochemical analysis identified nestin-positive cells in 84% (35/42) of primary melanoma and 83% (10/12) of metastatic melanoma. Nestin immunoreactivity was also observed in melanoma cells in all (10/10) cases of HMB-45-negative amelanotic and melanotic, non-desmoplastic melanoma. Nestin expression has been reported in tumors of the CNS, including astrocytoma, ependymoma, oligodendroglioma, glioblastoma, and primitive neuroectodermal tumors. Nestin has been detected in human gliomas, including low and high grade, but its expression is observed more frequently in high grade than in low grade gliomas. Nestin overexpression is seen in carcinomas, including prostatic adenocarcinoma, pancreatic ductal carcinoma, thyroid carcinoma, and in mesenchymal tumors such as GIST and DFSP. Among the breast carcinoma subtypes, nestin is highly expressed in basal breast cancer subtype (ERα-/PR-/Her2-) but not in the Her2 subtype (ERα-/PR-/Her2+) or luminal epithelial phenotype (ERα+/PR+). Only cytoplasmic staining is considered positive, whereas any nuclear staining is considered as background artifact. In normal skin, nestin is observed in endothelial cells and the bulge area of hair follicles.