Neuofilaments (NF) are members of the intermediate filament protein family. These neuron-specific filaments are the major constituents of the axonal cytoskeleton. They are also expressed in paragangliomas, adrenal pheochromocytomas, Merkel cell tumors, carcinoid tumors, neuroendocrine carcinomas of the skin, and small cell carcinomas of the lung. NFs are composed of three major proteins: NF-H is the heavy molecular weight protein (200 kDa), NF-M the medium (160 kDa) and NF-L the light protein (68 kDa). The NF-L and NF-M mRNAs are detected early in the embryonal brain, with a progressive increase in their levels during development, while the NF-H mRNA is barely detectable at embryonal stages but accumulates later in the postnatal brain. Anti-Neurofilament stains a variety of neural, neuroendocrine, and endocrine tumors, such as neuromas, ganglioneuromas, gangliogliomas, ganglioneuroblastomas, and neuroblastomas. It is a useful for the identification of tumors with neuronal differentiation.