Neuronal tumors

Neurofilaments stain both tests for a ganglionic tumor component (see the Neuronal Tumors section later in this chapter) and often show axons of brain tissue that existed before the tumor.The latter helps assess infiltration by neoplastic cells. 

Neuronal tumors contain an abnormal proliferation of neurons. They range from the most benign ganglio-cytoma to the anaplastic ganglioglioma and primitive... 

While neuron-specific enolase (NSE) has been described as a marker of neuronal tumors in reviews and texts, this author finds that it has better uses than this. The shortcoming for neuronal tumors is its propensity to also stain glial tumors, which commonly need to be distinguished from neuronal tumors. 7 Experimental IFIC stains such as Neu-N identify neurons by showing their on-target nuclear features rather than their cytoplasmic or confusing surface features. " 425 cases refractory to immu-nohistochemical stains, electron microscopy positively identifies Nissl substance, neurofilaments, neurosecretory granules, and synapses in neoplastic cells. 

Key markers of neuronal tumors are synaptophysin and neurofilaments. High-quality hematoxylin counterstain is needed to reveal neoplastic nuclei in positive cells. 

Many neuronal markers including NSE are not reliably specific for neuronal tumors. Test new markers on gliomas before using them to identify neuronal tumors. 

Cortical dysplasia consists of disrupted cortical architecture and abnormally enlarged cells, some with IFIC staining of neurons, some with GFAP-positive astrocytes, and some individual cells that stain for both glial and neuronal markers.Cortical tubers, seen with tuberous sclerosis, are cortical dysplasias. Other dys-plastic abnormalities are described in the Neuronal Tumors section earlier in this chapter. 

Figarella-Branger D, Pellissier JF, Daumas-Duport C, et al. Central neurocytomas Critical evaluation of a small-cell neuronal tumor. Am J Surg Pathol. 1992 16 97-109. 

Extrahypothalamic OX-B-like immunoreactivity, reminiscent to that of CRF, has been described in clustered GABAergic neuronal populations, in the lateral division of central nucleus ofthe amygdala, the bednucleus of the stria terminalis, and in the hippocampus. Moreover, ectopic expression of preproorexin mRNA in the gut, ependymal cells, neuroblastomas, and of orexin receptors in adrenal gland, cancer and hematopietic stem cells suggests yet unexplored roles of orexins as paracrine factors controlling blood-brain barrier, and tumor or stem cell function. 

Many environmental toxins interact with specific cellular receptors, including enzymes, ion channels and ion pumps, and thus provide natural tools for the study of cellular signalling pathways. Palytoxin, a compound isolated from the coelen-terate of genus Palythoa, is one such useful and intriguing compound. The structure of palytoxin was first determined in 1981 independently by Hirata (7) and Moore (2). As one of the most potent marine toxins known, palytoxin has been studied in a variety of systems ranging from erythrocytes to neurons. As a tumor promoter of the non 12-O-tetradecanoylphorbol-13-acetate (TPA) type, palytoxin can also be studied in the context of a growth control system. 

Fig. 4.4 Simplified hypothesis of the mechanism of gpI20-induced dorsal root gangUon (DRG) neurotoxicity. CXCR4 binding on Schwann cells by SDF-Ia or gpI20 results in the release of RANTES, which induces tumor necrosis factor (TNF)-a production by DRG neurons, and subsequent TNFRl-mediated neurotoxicity in an autocrine/paracrine fashion. Reproduced with permission of John Wiley Sons, Inc. (Keswani et al. 2003b)...

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