Pathology of the Head and Neck

86 J.W. Eveson3shredded, often patchily erythematosus white plaqueslimited to areas accessible to chewing. In typical frictionalkeratosis microscopy usually shows a thick orthokeratinisedlayer with a prominent granular cell layer.There is no significant dysplasia and inflammation ofthe underlying corium may be minimal in the absenceof ulceration. In keratosis due to habitual chewing thereis often acanthosis and the surface is usually irregularand parakeratinised. It frequently shows a covering ofadherent basophilic cocci or more dense bacterial conglomerates.Fig. 3.11. Geographical tongue (erythema migrans) showingpolymorphonuclear leukocyte microabscesses in the epithelium3.5 Pigmentationsreaction in the underlying corium. The striking featureis the presence of polymorphonuclear leukocytic microabscessesin the upper stratum spinosum (Fig. 3.11).These spongiform pustules are not pathognomonic ofgeographical tongue and can be seen in oral psoriasis,acute and chronic candidosis, Reiter syndrome and plasmacell gingivostomatosis. Some describe elongation ofthe rete ridges, but this is by no means a consistent observation.However, occasionally there may be psoriasiformhyperplasia in geographical tongue and it may bedifficult or impossible to distinguish from psoriasis. Indeed,geographical tongue and migratory stomatitis are4–5 times more common in patients with psoriasis andsome believe that geographical tongue is the oral homologyof psoriasis [179, 194]. The presence of spongiformpustules in oral biopsies should always promptthe search for candidal hyphae with a PAS or Grocottstain. These are not usually seen in geographical tongueand their presence would make a diagnosis of candidosismuch more likely. Chronic hyperplastic candidosis canalso show psoriasiform hyperplasia, but typically thereis much more florid inflammatory infiltration of the coriumand irregular surface parakeratosis.3.4.10 Frictional KeratosisFrictional keratosis of the oral mucosa is common and isusually a response to low-grade irritation by such causesas sharp edges of teeth or restorations, dental prostheses,abrasive foods, vigorous tooth brushing and playingwind instruments.Clinically, the lesions tend to form diffuse keratoticplaques. In the early stages these are pale and translucentand merge imperceptibly into the surrounding normalmucosa. Later, they become more dense and whiteand may have an irregular, shaggy surface. The habit ofcheek, lip and tongue chewing is a usually characteristicvariant of frictional keratosis. It results in roughened or3.5.1 Amalgam TattooAmalgam tattoo is the most common localised form oforal mucosal pigmentation [23]. Lesions usually formpainless, bluish-black macules, which may be well definedor diffuse, and the most common sites are the gingiva,alveolar mucosa and floor of the mouth. They arecaused by ingress of dental amalgam through a mucosalbreach during a restorative procedure or tooth extractionand can also follow an apicectomy with retrograderoot filling.Microscopy shows dark, refractile particles of amalgamin the corium [44]. These may be coarse, but usuallyform fine, black or brownish granules. These aredeposited along collagen and elastic fibres, and aroundsmall blood vessels, nerves and muscles. About half ofcases show a fibrous and chronic inflammatory reaction,with or without multinucleated foreign body giantcells. Occasionally, there is a granulomatous reaction.3.5.2 Localised Melanotic Pigmentation3.5.2.1 Oral Melanotic MaculesThese benign, ephelis-like pigmented macules are themost common melanocytic lesions of the oral mucosa.They are brownish-blue or black and may be single ormultiple. They are typically well defined and rarelyexceed 6 mm in diameter. They develop during earlyto middle adult life with a mean age at presentation of41 years [22]. There is a female predilection of 2:1. Theyare most frequent in the anterior part of the mouth affectingthe gingiva, buccal mucosa and, most commonly,the labial mucosa. Those involving the vermilion border(labial melanotic macules) often darken in strong sunlightand may cause cosmetic problems. Oral melanoticmacules have been reported following radiotherapy [11],