Pathology of the Head and Neck

Nasal Cavity and Paranasal Sinuses Chapter 2 59Table 2.3. Olfactory neuroblastoma. Hyams Grading Scheme [122].Histologic grades 1 2 3 4Lobular architecture Present Present ± +Mitotic activity Absent Present Prominent MarkedNuclear pleomorphism Absent Moderate Prominent MarkedFibrillary matrix Prominent Moderate Slight AbsentRosettes H-W + H-W + Flexner + AbsentNecrosis Absent Absent Occasional CommonCalcification ± + Absent AbsentH-W Homer-Wright rosettes, + present or absentabFig. 2.13. Primitive neuroectodermal tumour (PNET). a Monotonousproliferation of small, round, undifferentiated cells. bCD99-positive immune reaction at the cellular membranedepict different histological patterns that may be predominantlypapillary, glandular, compact, mucinous or mixed[17, 23]. Papillary tumours mainly consist of elongatedoutgrowths lined by intestinal-type cells with markedlyatypical pseudostratified nuclei (Fig. 2.14a). Althoughmost of them are high-grade tumours, low-grade forms(Fig. 2.14b) mimicking colonic villous adenoma may occasionallyoccur [174]. The glandular pattern resemblescommon-type intestinal adenocarcinoma. Compact orsolid forms show poorly differentiated nests of cells inwhich glandular formation is rarely seen. In the mucinouspattern, more than 50% of the tumour is composedof dilated mucin-filled glands lined by columnar mucin-secretingepithelium, and lakes of mucin containingfragmented epithelial elements (Fig. 2.14c). Other mucinoustumours show mucin-filled cells with the pattern of“signet-ring” cell carcinoma. Various attempts have beenmade to correlate histopathological grading and typingwith clinical behaviour [78, 81, 140].Features such as cytologic atypia, high mitotic rate andareas of necrosis, which are common findings in most intestinal-typeadenocarcinomas, help to distinguish thehigh-grade variants from rare low-grade intestinal-typeadenocarcinomas and from mucoceles. The lack of epidermoidand squamous differentiation separates these tumoursfrom mucoepidermoid and adenosquamous carcinomas.Immunohistochemistry and electron microscopyhave confirmed the enteric differentiation of the tumourcells [24]. These tumours are positive for a wide spectrumof cytokeratin markers, whereas they are only occasionallypositive for carcinoembryonic antigen [166]. Intestinal-typeadenocarcinomas are frequently but not alwayspositive for cytokeratin 7, while most express cytokeratin20 and CDX-2, two markers related to intestinal differentiation[79]. The prognosis for high-grade intestinal-typeadenocarcinoma is poor. Recurrences and subsequentdeeply invasive local growth are frequent; however,lymph node and distant metastases are rare [17, 78,142]. Treatment of choice is complete surgical resectionfollowed by radiotherapy.2.11.9.2 Salivary-TypeHigh-Grade AdenocarcinomasAdenoid Cystic CarcinomaICD-O:8200/3Adenoid cystic carcinoma (see Chap. 5) is the most commonmalignant salivary-type of tumour of the upper