Pathology of the Head and Neck

Major and Minor Salivary Glands Chapter 5 135only occasionally in the parotid (see Sect. 5.8.10). Thelesions are often multifocal and usually small, but canreach 30 mm in diameter.5.6.3 Multifocal NodularOncocytic HyperplasiaThis rare condition consists of nodules of varying size,composed of oncocytic cells, often with relatively clearcytoplasm. The nodules appear to engulf normal acinigiving a false impression of invasion, but there is nostromal or other response by the acini. Multifocal nodularoncocytic hyperplasia (MNOH) can be mistaken fora clear cell neoplasm with satellite deposits when onenodule is much larger than the others. MNOH can alsobe bilateral, and it has been reported to co-exist with apleomorphic adenoma, which itself showed oncocyticchange [20, 158].lobular architecture, and some lobules are affectedmore severely than others. The cysts vary in size up toa few millimetres, and they are irregular in shape andoften interconnect. The lining epithelium is flat, cuboidalto low columnar, sometimes with an apocrinelikeappearance. The lumen contains secretion withspherical microliths. Remnants of salivary acini areseen between the cysts, and thick fibrous interlobularsepta are often prominent.5.7.2 MucocelesA mucocele is defined as the pooling of mucus in a cysticcavity [62]. Two types are recognised – extravasationand retention; extravasation mucocele is described inSect. 5.2.1. Retention cysts can occur at any age, and themucus pool is within an epithelium-lined cavity, likelyto be a dilated excretory duct.5.7 CystsNon-neoplastic cysts and pseudocysts accounted forabout 6% of all lesions of the salivary glands in the Hamburgregistry of salivary neoplasms and tumour-like lesions[172]. They can be classified as:1. Dysgenetic, e.g. polycystic dysgenetic disease;2. Acquired cysts lined with epithelium, e.g. lymphoepithelialcystic lesions, duct cysts;3. Pseudocysts without an epithelial lining, e.g. extravasationmucocele, including ranula;4. Cystic change in neoplasms, e.g. Warthin, variantsof mucoepidermoid and acinic cell carcinomas, lymphoepithelialsialadenitis (LESA), lymphoma, andrarely, pleomorphic adenoma;5. Miscellaneous other cysts.The commonest are mucoceles, including ranula (80%),parotid duct cysts (11%), lymphoepithelial cystic lesions(7%) and dysgenetic cysts and congenital sialectasia (together2%).5.7.1 Salivary PolycysticDysgenetic DiseaseThis very rare condition resembles cystic anomalies ofother organs, such as the kidney, liver and pancreas,although no association has been described [62, 172,177]. Some cases are familial [207], and almost allcases occurred in females. Most patients present inchildhood, but some have not been recognised untiladulthood. It only affects the parotid glands, usuallybilaterally. Microscopically, the glands maintain their5.7.3 Simple Salivary Duct CystsSalivary duct cysts are acquired, and are due to dilatationof a salivary duct following obstruction, sometimesby a tumour [62]. They can occur at any age, althoughusually in patients over 30 years old. Most (85%) arisein the parotid and are unilateral and painless. They arewell-circumscribed, unilocular and up to 100 mm in diameter(usually 10 to 30 mm). They contain fluid that iswatery to viscous brown, occasionally with mucus. Thewall comprises dense fibrous tissue, 1–3 mm thick, andthere is often mild to moderate chronic inflammation,although not the dense lymphoid infiltrate of a lymphoepithelialcyst. The epithelium is stratified squamous, ora single layer of cuboidal or columnar cells, with occasionalgoblet cells and oncocytes.5.7.4 Lymphoepithelial Cystic LesionsSeven types of salivary lesions can be characterised bysingle or multiple epithelial-lined cysts surrounded bylymphoid tissue including germinal centres: benignlymphoepithelial cyst and cystic lymphoid hyperplasiaof AIDS, in addition to Warthin’s tumour, LESAand mucosa-associated lymphoid tissue (MALT lymphoma)each with cystically dilated ducts, low-gradecyst-forming mucoepidermoid carcinoma with a heavylymphocytic response, and cystic metastases in intraparotidlymph nodes, each of which is discussed inSect. 5.14.