Pathology of the Head and Neck

Eye and Ocular Adnexa Chapter 10 303berculosis, mumps, malignant lymphoma and syphilis.The most frequent cause of Mikulicz syndromeis Mikulicz disease; the histology is similar to that ofbenign lymphoepithelial lesions seen in the salivaryglands. Acute and chronic dacryocystitis and canaliculitisare the result of inflammation, mostly nonspecific,of the lacrimal passages. It may lead to dacryolithiasis(stones in the lacrimal sac) and to lacrimalmucocele.10.6.2 Tumoursand Tumour-Like ConditionsIf a mass is found in the superolateral quadrant of theorbit, dermoid cysts and lacrimal gland masses shouldbe considered. Fifty percent of lacrimal gland tumoursare pleomorphic adenomas and the other half are malignant[27, 98, 134]. The malignant category includes predominantlyadenoid cystic, carcinoma ex pleomorphicadenoma and mucoepidermoid carcinoma. The lacrimaltumours have few distinguishing imaging features,showing mostly a homogeneous character and moderatecontrast enhancement. Poorly defined margins withbone destruction suggest a malignancy, but even themalignant lesions can be relatively well defined. Thehistology of lacrimal gland tumours is similar to that ofsalivary gland tumours as discussed in Chap. 5. Papillomasand squamous cell carcinomas are the benign andmalignant tumours most commonly seen in the lacrimalsac. Their microscopic features are similar to those arisingfrom the mucosa of the nose (see Chap. 2) or in theconjunctiva.10.7 Eyelids10.7.1 CystsBecause of the numerous adnexal glands present in theeyelids, cysts are very common at this localisation. Thecysts can be of developmental origin (dermoid cysts) orcan be caused by inclusion or retention.10.7.1.1 Dermoid CystThe most common type of a cyst of the eyelids in childrenis the dermoid cyst, a developmental cyst caused byinclusion of ectodermal rests within the lines of closureof the branchial arches. Dermoid cysts are lined withstratified squamous epithelium with small pilosebaceousunits attached to the wall (Fig. 10.26). The lumenusually contains small hairs and keratin. The presenceFig. 10.26. Dermoid cyst: lined with squamous epithelium withsmall pilosebaceous units in the wallof pilosebaceous units differentiates this cyst from epidermalcysts.10.7.1.2 Epidermal cystsEpidermal cysts (epidermoid cysts, keratinous cysts) arefirm, often yellow-brown masses, diagnosed clinicallyas “sebaceous cysts”. However, real sebaceous cysts (steatocystomas)are very rare and most cysts will histologicallyshow a lining with stratified squamous epitheliumwithout pilosebaceous glands. The cysts are filled withstrands of keratin. Epidermal cysts can be caused bydermal inclusion of epithelial cells after a microtrauma,but also by occlusion of a pilosebaceous unit. If an epidermalcyst ruptures, keratin will be released betweenthe collagen bundles of the dermis, causing a granulomatousforeign body reaction.10.7.1.3 HidrocystomaCysts derived from the small sweat glands present inthe eyelids present as bluish, round lesions and areclinically often misdiagnosed as haemangiomas. Theterm hidrocystoma is preferred, but many other names,like cysts of Moll’s glands and sudiferous cysts, can befound in the literature. The eccrine cysts are lined withcuboidal to flattened epithelium with a myoepithelialbase (Fig. 10.27). Sometimes only one epithelial layeris visible, showing eosinophilic cytoplasm with snouts,characteristic of apocrine differentiation. It can be veryhard to differentiate between eccrine or apocrine originsand sometimes both components can be found inthe cysts.