Pathology of the Head and Neck

Oral Cavity Chapter 3 85keratosis of the palate exposed to the smoke. This leadsto obstruction of the ducts of the underlying minor salivaryglands, which then become inflamed. The classicalclinical appearance, therefore, is whitening of the palatalmucosa, which may show tessellated plaque formation.The involved minor glands become swollen andhave red, umbilicated centres.Microscopy shows variable hyperkeratosis, acanthosisand duct dilatation. There is usually no evidence ofepithelial dysplasia. There is variable submucosal chronicinflammation and there may be evidence of pigmentaryincontinence. Keratinisation can extend down thesalivary ducts and there is interstitial inflammation ofthe underlying minor mucous glands.The condition will gradually resolve if the habit isdiscontinued and there appears to be minimal risk ofmalignant transformation. However, affected individualshave an increased risk of developing squamouscell carcinoma in other parts of the mouth, particularlythe floor of the mouth and adjacent ventral lingualmucosa, and the retromolar trigone. Conversely, palatalkeratosis due to “reverse smoking” where the lightedend of a cigarette or cigar is held in the mouth isassociated with the development of carcinomas of thehard or soft palates in a very high number of patientspractising the habit [148].3.4.7 Hairy TongueHairy tongue is due to hyperplasia and elongation ofthe filiform papillae, which form hair-like overgrowthson the dorsum. The filaments can be several millimetreslong. The colour varies from pale brown to intenseblack. The discoloration is due to proliferation ofchromogenic bacteria and fungi. Hairy tongue is usuallyseen in older individuals, and smoking, antisepticmouthwashes, antibiotics and a diet lacking abrasivefoodstuffs are the most common predisposing factors.The dorsum of the tongue may also become blackenedwithout elongation of the filiform papillae byantibiotic mouthwashes such as tetracycline and ironcompounds. Hairy tongue is rarely biopsied. Microscopically,it is characterised by irregular, hyperplasticfiliform papillae showing hyperorthokeratosis or hyperparakeratosiswith numerous bacterial conglomeratesand filamentous organisms in the surface layersand more deeply between fronds of epithelium. It hasbeen shown by immunocytochemical analysis of keratinexpression that in black hairy tongue there is defectivedesquamation of cells in the central column ofthe filiform papillae. This results in the typical highlyelongated, cornified spines that are the characteristicfeature of the condition [110].3.4.8 Hairy LeukoplakiaPatients infected with HIV, particularly homosexualmales, may develop characteristic intraoral white lesions[149]. The lateral margins and underlying ventrum ofthe tongue are the most common sites. The lesion wascalled hairy leukoplakia, but typically it forms painless,vertical, white corrugations that may or may not havea rough or “hairy” surface. Some lesions are flat whiteplaques. Other sites may also be involved, especially thepost-commissural buccal mucosa.Microscopy shows acanthosis and parakeratosis,usually with verruciform, hair-like surface projections[168]. Invasion of the surface epithelium by candidal hyphaeis common. Immediately below the parakeratoticlayer there is a zone of vacuolated and enlarged epithelialcells with intense basophilic, pyknotic nuclei and perinuclearclearing (koilocytes). Epstein-Barr capsid viralantigen and viral particles can be demonstrated in thekoilocytic nuclei [172]. There is usually little or no inflammatoryinfiltration of the epithelium or underlyingcorium. Similar lesions have occasionally been reportedin patients receiving immunosuppressant drugs followingorgan transplantation. The early cases of hairy leukoplakiaassociated with HIV infection showed a veryhigh rate of progression to full-blown AIDS. Lesions canresolve spontaneously and usually respond well to antiviralor anti-retroviral drug treatment; they appear tohave no premalignant potential.3.4.9 Geographic TongueGeographic tongue is a relatively common idiopathiccondition typically characterised by migrating areas ofdepapillation on the dorsum of the tongue [6]. In manycases it is associated with fissuring. There is loss of filiformpapillae often surrounded by a slightly raisedyellowish-white and crenellated margin. These areasof depapillation tend to heal centrally and spread centrifugally.Occasionally, the ventrum is involved and inthat site lesions consist of an area of erythema completelyor partially surrounded by a circinate whitish halo.Identical lesions can occasionally be seen elsewhere inthe mouth and have been called “ectopic geographicaltongue”, although geographical stomatitis or benignmigratory stomatitis would be more appropriate terms[81]. The majority of cases of geographical tongue arepainless, but some patients complain bitterly of sorenessand discomfort, which may or may not be associatedwith specific foods.Geographical tongue is usually obvious clinicallyand is rarely biopsied. However, it has very typical microscopicalfeatures [114]. There is loss of filiform papillaeand typically only a mild chronic inflammatory