Paraganglioma is a benign neoplasm made up of cells originating from the neural crest and later migrating together with ganglionic cells of the autonomic nervous system. Histologically, the lesion is characterized by nests of epithelioid cells (Zellballen), surrounded by a capillary network (Shanmugaratnam 1991). Other terms such as glomus tumor, chemodectoma and apu-doma have been used, but at present paraganglioma is the recommended name. Paragangliomas are commonly divided into adrenal (i.e., pheochromocytomas) and extra-adrenal in relation to the site of origin. The latter group includes cervicofacial paragangliomas, which rarely secrete catecholamines and therefore are classified as non-chromaffin. Most cases take origin in the temporal bone (glomus jugulare and glomus tym-panicum), above the bifurcation of the carotid artery (carotid body), and from the nodose ganglion (glomus intravagale) (Lack et al. 1977), whereas localization in the sinonasal tract is exceedingly rare, with approxi-
mately 30 cases reported in the literature (Ketabcm et al. 2003). In this area, the lesion more frequently involves the ethmoid and the middle turbinate; furthermore, there is a slight predominance in females and in the fifth decade of life (Ketabcm et al. 2003).
As in other anatomic sites, paraganglioma of the si-nonasal tract may display an aggressive behavior and an infiltrating growth pattern (Welkoborsky et al. 2000). According to a recent review of the literature (Ketabcm et al. 2003), six patients with paraganglioma of the si-nonasal tract presented distant or regional metastases. Increased mitotic figures, necrosis, vascular invasion, aneuploidy and a high proliferation rate may be important indicators for identifying lesions with a potentially aggressive biological behavior (Shanmugaratnam 1991; Welkoborsky et al. 2000)
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