Pathology of the Head and Neck

Major and Minor Salivary Glands Chapter 5 143Fig. 5.17. Warthin’s tumour. Cystic and slit-like spaces with papillaryinfolding lined with oncocytic cells. Lymphoid tissue occupiesthe cores of most papillaeFig. 5.20. Canalicular adenoma of the upper lip. It is composedof bi-layered strands of basal-like cells embedded in a loose oedematousstromathelial markers are negative. Histological variants includea stroma-poor form, and metaplastic WT – inthe latter, much of the original oncocytic epitheliumhas been replaced by squamous cells, and there is extensivenecrosis, fibrosis, inflammation, and granulomaformation (Fig. 5.18) [66]. This not uncommonlesion follows trauma, particularly FNA [55], and canbe mistaken for squamous or mucoepidermoid carcinomas(see Sect. 5.5.5). WT generally has a good outcome,with recurrence rates of about 2%. Malignancyoccurs in less than 1% of cases, involving either epithelialor lymphoid elements leading to carcinomas orlymphomas [62].Fig. 5.18. Metaplastic (infarcted) Warthin’s tumour. There is extensivenecrosis. A surrounding thin rim of viable tissue showssquamous metaplasia5.8.5 OncocytomaICD-O:8290/0Oncocytic change in salivary tumours is common (seeSect. 5.6) [65]. Oncocytoma is a true benign neoplasmcomposed of oncocytes. It is rare and is often associatedwith MNOH (see Sect. 5.6) [158]. It comprises awell-demarcated mass of oncocytic cells (both light anddark) with a solid, trabecular, or tubular configuration(Fig. 5.19). There is a surrounding, usually incompletefibrous capsule, and only a little internal fibrous stroma.There is a rare clear cell variant [61].5.8.6 Canalicular AdenomaFig. 5.19. Oncocytoma. Light and dark oncocytic cells are arrangedin a solid, trabecular and tubular configurationICD-O:8149/0Canalicular adenoma also has a basaloid appearance.Its location is almost exclusively intraoral, particularlyaffecting the upper lip [119] and less often thepalate. As a result, most tumours present when small