Pathology of the Head and Neck

4 N. Gale · N. Zidar1An exact and uniform terminology of SILs is a prerequisitefor successful cooperation among pathologists aswell as adequate understanding with clinicians. A considerableoverlapping of clinical and histological termsrelating to SILs has been widely noticed due to inadeaFig. 1.4. Laryngeal papillomatosis. a Branches of laryngeal papillomaare covered with hyperplastic squamous cell epithelium. Numerouskoilocytes are seen in the upper part of the epithelium.bb Positive in situ hybridisation signal for HPV genotypes 6 and 11in an adult laryngeal papillomamas [301, 330]. The presence of RRP in the neonatal periodis a negative prognostic factor with a greater needfor tracheotomy and likelihood of mortality [88]. Onereport on the spontaneous disappearance of the disease,especially during puberty, has not been further supported[4]. Increased histologic changes (atypia of epithelialcells) are reported to be associated with increased severityand recurrence of RRP [75, 288]. Others have suggestedthat the histologic changes of RRP are not a goodpredictor of eventual malignant transformation [133].Malignant transformation occurs mainly in patientswith a history of previous irradiation or heavy smoking[290], and rarely without any predisposing factors[143, 296]. In children, carcinomas preferentially appearin the bronchopulmonary tree, and in adults in the larynx[141]. HPV genotype 11 is assumed to be most frequentlyassociated with malignant transformation ofRRP [70, 206, 218, 290], followed by HPV-16 [92] andHPV-18 [311].The overall mortality rate of patients with RRP rangesfrom 4 to 14% [20], and is mostly causally related toasphyxia, pulmonary complications and cancer development[17, 20, 338].1.2 Squamous Intraepithelial Lesionspression of the whole spectrum of epithelial changesranging from squamous cell hyperplasia to carcinomain situ.It has been widely accepted that the transition fromnormal mucosa to invasive squamous cell carcinoma(SCC) is a comprehensive and multistage process, causallyrelated to a progressive accumulation of geneticchanges leading to the selection of a clonal population oftransformed epithelial cells [144]. Between six and tenindependent genetic events are required for progressionto SCC [300]. In their evolution, some cases of SIL areself-limiting and reversible, some persist, and some ofthem progress to SCC in spite of treatment [78]. Particularinterest has been focused on potentially malignantor risky (precancerous) lesions [48, 181, 200, 223]. Theselesions have been defined as histomorphological changesof the squamous epithelium from which invasive cancerdevelops in a higher percentage than from other epitheliallesions [125, 179, 181, 223]. A fundamental enigmaof potentially malignant lesions remains when andunder what conditions these changes turn to malignantgrowth [180, 223].Various aetiological, clinical, histological and moleculargenetic aspects are significant for the evaluation,adequate treatment and predictive behaviour of SILs,particularly of potentially malignant lesions.1.2.1 General ConsiderationsHistological changes of the squamous epithelium thatoccur in the process of oral, oro- and hypopharyngealand laryngeal carcinogenesis, are cumulatively designatedsquamous intraepithelial lesions (SILs). Theterm SILs has been proposed as an all-embracing ex-1.2.2 Terminological Problems