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Definition, Epidemiology, Pattern of Growth

Sinonasal neuroendocrine carcinoma and sinonasal undifferentiated carcinoma are two rare and aggressive malignancies, which have been only in recent years recognized and categorized. They share the prevalent site of origin (i.e., superior part of the nasal cavity, upper ethmoid) as well as some imaging, clinical and histological features. Both the identification and the distinction of the two histotypes require an evaluation of the immunohistochemical profile (Smith et al. 2000), which is otherwise essential for the differentiation from other malignant neoplasms such as olfactory neuroblastoma, lymphoma, Ewing's sarcoma, and melanoma.

Sinonasal neuroendocrine carcinoma, first identified by Silva et al. (1982), is supposed to take origin from submucosal glands (Smith et al. 2000). Most neuroendocrine carcinomas occur in the lung, but an extra pulmonary origin from several anatomic areas is possible (Westerveld et al. 2001). In the head and neck, the most common site of origin is the larynx, with only a few cases involving the sinonasal tract. The immunohistochemical profile shows positivity a

Fig. 9.25a,b. Olfactory neuroblastoma arising from left ethmoid. The perpendicular plate is displaced towards the left, the mass projects inferi-orly down to the level of the horizontal middle turbinate. Laterally, the tumor spreads through the vertical lamella of the middle turbinate. The lesion contacts both the horizontal and vertical laminae of the cribriform plate. b Blockage of the small left sphenoid sinus results in mucus filling. Permeated invasion of the ethmoid cells is present

Fig. 9.25a,b. Olfactory neuroblastoma arising from left ethmoid. The perpendicular plate is displaced towards the left, the mass projects inferi-orly down to the level of the horizontal middle turbinate. Laterally, the tumor spreads through the vertical lamella of the middle turbinate. The lesion contacts both the horizontal and vertical laminae of the cribriform plate. b Blockage of the small left sphenoid sinus results in mucus filling. Permeated invasion of the ethmoid cells is present b a for neuroendocrine markers such as neuron specific enolase, chromogranin A, synaptophysin and also for other markers as Cam 5.2 and AE1:AE3; conversely, S-100 and neurofilaments are usually negative (Perez-Ordonez et al. 1998). Although the neoplasm has been described at any age between 16 and 77 years, the prevalent distribution is in the fifth and sixth decade (Perez-Ordonez et al. 1998; Smith et al. 2000).

First described by Frierson et al. (1986), sinona-sal undifferentiated carcinoma consists of undiffer-entiated cells supposed to derive from schneiderian epithelium or nasal ectoderm (Greger et al. 1990). The immunohistochemical evaluation shows posi-tivity for cytokeratin, epithelial membrane antigens, and possible positivity for neuron specific enolase, whereas vimentin and S-100 protein are usually negative (Goreliok et al. 2000). Sinonasal undiffer-entiated carcinoma is usually diagnosed in the sixth decade of life, with a range between 31 and 81 years (Musy et al. 2002).

Due to their aggressiveness, both sinonasal neuroendocrine and undifferentiated carcinoma tend to early involve adjacent bony structures, with invasion of soft tissue, orbit and anterior cranial fossa (Kim et al. 2004).

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