Pathology of the Head and Neck

90 J.W. Eveson3.5.9 Drug-AssociatedOral Pigmentation3Gingival pigmentation due to heavy metals such asmercury, lead, bismuth, arsenic and others was notrare in the past due to industrial exposure and in somecases therapeutic administration, particularly for thetreatment of syphilis. They caused blue, brown orblack lines close to the gingival margins due to the depositionof sulphides as a result of reactions with productsof the dental plaque. A wide range of drugs cancause more generalised oral pigmentation includingantimalarials, phenothiazines and some contraceptivepills [98]. Drugs used in the treatment of HIV infectionsuch as zidovudine and some antifungals such asketoconazole have also been shown to cause oral pigmentation.3.6 Hyperplastic Lesions3.6.1 Fibrous HyperplasiasThe majority of fibrous and fibroblastic lesions withinthe mouth appear to be reactive rather than neoplastic.They are the most common tumour-like swelling of oralmucosa. Although these lesions are considered to be aresponse to low-grade irritation, the source of such irritationmay not be immediately apparent. Fibroepithelialpolyps tend to form smooth nodules or swellings thatmay be soft or firm and are usually covered by normal,pink mucosa unless ulcerated. The polypoid swellingsmay be sessile or pedunculated.Fibrous overgrowths of the gingiva are a type of epulis(lit. – swelling of the gum). They can arise from theinterdental papilla or gingival margin and tend to affectthe anterior part of the mouth. They can grow to severalcentimetres in diameter. Fibrous epulides are frequentlyassociated with local irritation from dental calculus,sharp edges of restorations or carious teeth. A very characteristicform of hyperplasia is associated with the edgesof loose dentures. Such denture-induced fibrous hyperplasiahas been termed denture granuloma and epulisfissuratum. The rocking backwards and forwards ofthe denture causes extensive overgrowth of fibrous tissueon either side of the edges, or flanges, of the denture.This often leads to the formation of a series of linearfolds of hyperplastic tissue and the base of the groovesso formed is often ulcerated by the denture’s edge. Othercommon sites for fibrous overgrowths are along theocclusal line of the buccal mucosa and lateral border ofthe tongue, and related to spaces where teeth have beenextracted.Microscopically most of these nodules consist of interlacingbundles of sparsely cellular fibrous tissue. TheFig. 3.15. Fibrous epulis showing osseous metaplasiaoverlying epithelium is often hyperplastic with irregularrete processes extending sometimes deeply into the underlyingfibrous tissue. There may be candidal infestationof the superficial epithelium. The degree of inflammatoryinfiltration is very variable, but tends to be mildunless there has been ulceration.The microscopical appearances of fibrous epulidescan differ from fibrous overgrowths seen elsewhere inthe mouth. They typically show much more evidenceof cellular fibroblastic proliferation. These lesions mayconsist predominantly or focally of a vascular stromacontaining plump fibroblasts with large, vesicular nucleiand prominent nucleoli. There can be brisk mitoticactivity. Ulceration is common and the lesions areoften heavily inflamed. Calcifications are common infibrous epulides and there may be florid osseous metaplasiaor dystrophic calcification (Fig. 3.15). Sometimesthe calcified masses are basophilic and they canalso be laminated and resemble cementicles. Such lesionshave been termed “peripheral ossifying fibromas”,but there is no evidence that they are neoplasticor have any relationship with central ossifying fibromas(see Chap. 4). Mineralisation tends to be uncommonin extra-gingival oral fibrous overgrowths.Most fibrous overgrowths respond to conservativesurgical removal, but a minority of fibrous epulides canrecur, sometimes repeatedly.3.6.2 Papillary HyperplasiaPapillary hyperplasia is typically seen in the hard palate.In many cases it is related to dentures as part of theclinical spectrum of denture-induced stomatitis [174].Although Candida albicans is frequently invoked as thecausal agent, in a significant number of cases there is noevidence of fungal infection. The large majority of casesinvolve the hard palate, particularly when this is higharched,but similar lesions are occasionally seen on thedorsum of the tongue. The lesions form painless, nodu-