Pathology of the Head and Neck

292 M.R. Canninga-Van DijkFig. 10.15. Malignant melanoma: detail of the nested, atypicalmelanocytes without maturation in the stromaFig. 10.16. Mucopolysaccharidosis: this cornea showed no abnormalitieson H&E staining, but colloidal iron showed deposits ofmucopolysaccharides very clearly1010.3 CorneaInflammation and ulceration of the cornea can becaused by trauma, surgery to the eye, infectious diseasesand systemic diseases. The trauma can be mechanical,chemical or caused by heat or irradiation. The increasingincidence of cataract extraction has led to an increasein cases with corneal damage during the surgical procedure.Infectious keratitis can be viral, bacterial, fungalor parasitic. In chronic granulomatous keratitis, causeslike leprosy, syphilis and tuberculosis should be considered.Especially in immunocompromised patients infectiouscauses should be excluded by additional stainslike PAS, Grocott and Gram. In corneal ulcers withouta clear aetiology, artificial keratitis has to be considered.Factitious injury is rare and can be either the result ofmechanical trauma or the abuse of toxic eye drops [26].Histology of factitious lesions is non-specific. An exampleof a systemic disease affecting the cornea is mucopolysaccharidosis(Fig. 10.16).10.3.1 Keratitisand Corneal Ulcersor punctate spots (punctate keratopathy). If the diseaserecurs, the virus may infect stromal keratocytes, causingchronic destruction with ulceration. Histologically,an early herpetic ulcer shows multinucleated epithelialcells with intranuclear viral inclusions. DNA in situhybridisation, immunohistochemistry and PCR aremodern techniques replacing the transmission electronmicroscopy that was used to demonstrate theherpes virus particles in earlier days [49]. In end-stagedisease, epithelial changes are no longer present; thereis just fibrosis with scarring. Often, Bowman’s layer isfocally replaced by fibrosis.10.3.1.2 Corneal UlcerationDue to Systemic DiseaseSystemic vasculitides like systemic lupus erythematosus,polyarteritis nodosa and Wegener’s granulomatosiscan cause peripheral corneal ulceration due to vascularocclusion by immune complex deposition in thelimbal vessels [73, 85]. In rheumatoid arthritis cornealulceration can occur due to the release of collagenases[92].10.3.1.1 Herpes Simplex KeratitisType 1 herpes simplex virus is the most common causeof corneal disease. After primary infection of the lip,the virus remains latent in the sensory trigeminal ganglion.Transneural migration and proliferation of thevirus is triggered by stress, sunlight or cold. The virusparasitises the epithelium, leading to superficial epithelialloss in a branching pattern (dendritic ulceration)10.3.2 KeratoconusThis condition presents at puberty and has been foundin association with systemic disorders like Marfan’s syndrome,Down’s syndrome [52, 88], neurofibromatosis,Ehlers-Danlos syndrome [56, 94, 129] and atopic dermatitis[93, 109, 119]. It can also be seen in combinationwith ocular disorders like aniridia, cataract and retinitispigmentosa [11, 33, 53]. A progressive, non-inflamma-