Pathology of the Head and Neck

24 N. Gale · N. Zidar1Fig. 1.20. Nasopharyngeal carcinoma.a Islands of poorly differentiated carcinomabeneath the surface epithelium, with denselymphocytic infiltration of the stroma.b In situ hybridisation reveals Epstein-Barrvirus RNA transcripts in the nuclei of all tumourcellsabcarcinomatous components, and the involvement of thesurface epithelium exhibiting atypical hyperplasia, carcinomain situ, or invasive SCC.The presence of mucin in true glandular spaces helpsto distinguish ASCs from adenoid SCCs.Conventional SCCs invading or entrapping the normalsalivary or mucoserous glands can be confused withASC, especially in small biopsy specimens. In such cases,preservation of lobular gland architecture and lack ofsignificant atypia are observed, helping to distinguishconventional SCCs from ASCs.Finally, ASCs must be differentiated from necrotisingsialometaplasia, which is a benign condition. The histopathologicfeatures suggesting the diagnosis of necrotisingsialometaplasia are: surface ulceration, localisationin minor salivary glands, lobular architecture, partialnecrosis of the salivary gland, and squamous metaplasiaof the salivary ducts.ICD-O:8082/3Lymphoepithelial carcinoma (LEC) is a poorly differentiatedSCC or undifferentiated carcinoma, associatedwith dense lymphocytic stromal infiltration. It ismorphologically indistinguishable from nasopharyngealcarcinoma type 3 (WHO classification) [381]. Itwas originally described in the nasopharynx in 1921by Regaud and Reverchon [294], and independently bySchmincke [315]. Synonyms for LEC include lymphoepithelioma,nasopharyngeal-type carcinoma, Regaudand Schmincke-type lymphoepithelioma, and undifferentiatedcarcinoma. The specific features of the nasopharyngealcarcinoma are extensively discussed inChap. 6.Apart from the nasopharynx, it rarely occurs in otherlocations in the head and neck, such as the oropharynx,salivary glands, tonsils, tongue, soft palate, uvula,floor of the mouth, sinonasal tract, larynx and hypopharynx[67, 93, 120, 227, 392], as well as elsewherein the body including the lung, urinary bladder, uterinecervix, breast, skin and stomach [113].1.3.8.4 Treatment and PrognosisThe ASC has a more aggressive course than the conventionalSCC [131, 258, 313], with a tendency toward earlylymph node metastases, frequent local recurrences, andoccasional dissemination [192]. The reported 5-yearsurvival rate is between 13 and 25% [124, 131, 192].The treatment of choice is radical surgical excision.Irradiation alone has had poor results [124, 192, 313].Some reports indicate that radical surgery combinedwith irradiation may improve the survival rate [6].1.3.9.1 AetiologyNasopharyngeal carcinomas are aetiopathogeneticallyassociated with the Epstein-Barr virus (EBV; Fig. 1.20b)[265]. Apart from nasopharyngeal carcinomas, EBV hasbeen also implicated in the pathogenesis of LECs of thesalivary glands, as well as undifferentiated carcinomasof the stomach, lung and thymus [153, 160]. In contrast,it seems that EBV plays little, if any role in the pathogenesisof LEC in other locations in the head and neck [93,153, 227, 392].1.3.9 Lymphoepithelial Carcinoma1.3.9.2 Pathologic FeaturesThe LEC is composed of small clusters or aggregates(Schmincke pattern) or large syncytial masses (Regaudpattern) of cells. Tumour cells have oval or round ve-