Pathology of the Head and Neck

72 J.W. Eveson33.1 Embryonic Restsand Heterotopias3.1.1 Fordyce Granules/SpotsFordyce granules are ectopic sebaceous glands in theoral mucosa [39, 119]. They appear as soft, creamy whiteor yellowish spots or clusters, typically a few millimetresin diameter. They are symmetrically distributedand tend to increase in size and number with age. Themain site is the buccal mucosa, but they may also involvethe vermilion border and labial mucosa, particularly inthe upper lip. More rarely, the tongue, palatoglossal fold,tonsil and other intraoral sites may be affected, and thecondition can then be confused with other lesions. Microscopyshows typical sebaceous glands opening directlyonto the surface by short, keratinised ducts withno associated hair follicles.3.1.2 Juxtaoral Organ of ChievitzChievitz’s organ, or the bucco-temporal organ, isthought to be a vestigial neuroepithelial structure. It hasalso been suggested that the juxtaoral organ is an anlageof the parotid gland, or arises from Schwann cells thathave undergone squamous metaplasia [132]. It has beendemonstrated in neonates and children and can persistinto adult life [16]. The organ is usually found betweenthe temporalis muscle and the bucco-temporal fascia orpterygomandibular raphe, and is usually present bilaterally.It is seen fortuitously, generally in material takenfrom surgical resections, and is important as it can bemisinterpreted as a squamous cell carcinoma. Very rarecases have presented as tumours in the infratemporalfossa [83]. It is usually only a few millimetres in size andmicroscopically forms a multilobulated mass of discretecell nests that resemble squamous epithelium, but do notshow obvious keratinisation. Occasionally, the cells haveclear cytoplasm and form duct-like structures that maycontain mucin-negative colloid. The cell nests are associatedwith nerve fibres, particularly at the periphery, andthis may be mistakenly interpreted as a squamous carcinomawith perineural involvement, or sometimes mucoepidermoidcarcinoma and thyroid carcinoma [103].The central areas of the epithelial cell nests are positivefor cytokeratin 19 and most cell nests are positive forvimentin and weakly positive for epithelial membraneantigen. They are negative for S-100 protein, glial acidicfibrillary protein, and neuroendocrine markers suchas chromogranin, synaptophysin and neurone-specificenolase [132]. A similar appearance to the juxtaoral organhas rarely been described elsewhere in the mouth,including intraosseous locations [47].3.2 Vesiculo-Bullous Diseases3.2.1 Herpes Simplex InfectionsHerpes simplex is a common virus that often causessubclinical infections. It is, however, a cause of seriousand sometimes fatal illnesses in immunocompromisedpatients. In the orofacial tissues, clinically apparent infectionscan be primary or recurrent. The majority ofcases of oral infections are due to Herpes simplex type1, but an increasing proportion is being attributed toHerpes simplex type 2, which is typically more closelyassociated with genital infections. The virus is transmittedby close contact. Although in the past primaryherpes affected children most frequently, in Westernsocieties it is seen increasingly in young and middleagedadults.Primary herpes infection (primary herpetic gingivostomatitis)is characterised by widespread vesicular lesionsof the oral mucosa [183]. Any site may be involved,but the hard palate and the dorsum of the tongue arethe most common locations. The vesicles quickly ruptureto leave shallow, painful, sharply demarcated ulcersthat are 1–2 mm in diameter and have an erythematoushalo. Ulcers frequently coalesce to form more irregularlesions. Gingivitis is a very characteristic feature of primaryherpes. The gingivae are swollen and often strikinglyerythematous, even in the absence of frank ulceration.There is often conspicuous cervical lymphadenopathy,together with mild fever and malaise. Oral lesionsusually resolve spontaneously within 1–2 weeks.About a third of patients infected with Herpes simplex,either clinically or sub-clinically, are susceptible to recurrentinfections.It is uncommon for herpetic lesions to be biopsied(Fig 3.1). In the early stages there is intercellular oedemaand ballooning and vacuolisation of keratinocytesdue to intracellular oedema. This leads to intraepithelialvesiculation. Nuclei become enlarged, and occasionallybasophilic or eosinophilic nuclear inclusions witha clear halo ( Lipschutz bodies) can be identified. Cellsmay fuse to form multinucleated epithelial giant cells.The vesiculation is followed rapidly by epithelial necrosisand breakdown, leading to ulceration and more floridinflammatory infiltration.Herpes simplex virus can persist in a latent form inthe trigeminal ganglion and when re-activated causesrecurrent infections. These are typically seen at themucocutaneous junctions of the mouth or nasal cavity,and involvement of the lips, the most common site,is called herpes labialis. A variety of apparently disparatefactors can trigger re-activation, including thecommon cold (“fever blister”), exposure to sunlight,menstruation, stress and others. There is usually abrief prodromal burning or prickling sensation in the