Pathology of the Head and Neck

60 A. Cardesa · L. Alos · A. Franchi2aggressive tumour from the seromucous glands of theupper respiratory tract may occasionally occur. We haveseen one example of SDC originating in the maxillaryantrum, in which the characteristic ductal pattern, withcomedo-type necrosis, was only evident in the metastasesto the submandibular lymph nodes. The primarytumour was initially classified as adenocarcinoma nototherwise specified (NOS) due to the absence of convincingdiagnostic features [40]. Carcinoma ex pleomorphicadenoma may also occur in the sinonasal tract [110].ab2.11.10 Low-Grade SinonasalAdenocarcinomasLow-grade adenocarcinomas arising primarily withinthe sinonasal tract are an uncommon and heterogeneousgroup of tumours [23, 113, 139, 150]. Some ofthese neoplasms show apparent histological continuitywith the normal surface epithelium of the sinonasalmucosa, whereas others are of salivary gland origin. Allhave better prognosis and different clinical presentationthan their high-grade counterpart. With the exceptionof the well-differentiated, low-grade, adenocarcinomasof intestinal type, no correlation with occupational activitieshas been found in these tumours.2.11.10.1 Non-Salivary-TypeLow-Grade AdenocarcinomascFig. 2.14. Intestinal-type adenocarcinoma. a Papillary outgrowthof intestinal-like malignant epithelium. Destruction of sinonasalbone at the bottom. b Low-grade variant mimicking villous adenomaof the colon. c Mucinous variant mimicking mucocelerespiratory tract and constitutes 5–10% of all sinonasalmalignancies [43, 105, 206]. It is most common in themaxillary antrum, followed by the nasal cavity [60], althoughethmoid, sphenoid and frontal sinuses may alsobe involved [110, 169, 255].Other Salivary-Type High-Grade AdenocarcinomasWith the exception of adenoid cystic carcinoma, thesetumours are quite rare in the sinonasal region. Althoughmost salivary duct carcinomas (SDCs) arise from themajor salivary glands, the development of this highlyNon-salivary-type low-grade sinonasal adenocarcinomasare a distinctive group of tumours comprising well-differentiatedtubular or papillary structures, or a combinationof both. They are lined by a single layer of cuboidalor columnar cells that display uniform round or ovalnuclei, inconspicuous nucleoli, minimal cytologic atypiaand scarce mitotic figures. They are locally infiltrativeand have a tendency towards local recurrence [113].Different histological patterns may be recognised:papillary, glandular, mucinous, trabecular, cribriformand clear cell. The papillary pattern is characterised bycomplex papillary fronds lined by bland columnar cellsthat may occasionally mimic oncocytic (columnar) cellpapilloma. Quite similar tumours also develop in thenasopharynx [267]. The glandular pattern may simulateadenoma; nevertheless, the presence of closely packedglands, forming back-to-back arrangements, indicatesthe true malignant nature. Mucinous tumours have to bedistinguished from mucoceles and from mucinous adenocarcinomaof intestinal or salivary type [20, 224]. Thetrabecular pattern may resemble acinic cell carcinoma[200]. The cribriform arrangements have to be distinguishedfrom low-grade salivary duct carcinoma of salivaryglands [62]. The clear cell type has to be separatedfrom the salivary-type tumours with clear cells and