Pathology of the Head and Neck

Lesions of Squamous Epithelium Chapter 1 13up and avoidance of exposure to known risk factors isimportant due to the risk of malignant transformation[47, 263, 334]. Recurrences of high-risk SILs are not infrequentevents, being reported in 18% of lesions thathad been excised with free surgical margins [366]. If thesize or other clinical obstacles make surgical treatmentof oral SILs difficult, various antioxidants, such as betacaroteneand the retinoids, are most commonly used forchemoprevention [191].The occurrence of the higher grades (moderate andsevere dysplasia, atypical hyperplasia) of oral SILs isconsidered the most important risk of SCC development.The reported frequency of malignant transformationof OL ranges from 3.1% [373] to 17.5% [323]. Severallocations of OL, together with histological abnormalities,are linked with higher malignant transformation.The floor of the mouth is, thus, the highest risk site, followedby the tongue and lip [319].The clinical appearance of non-homogenous or speckledOL may correlate with the likelihood that the lesionwill show epithelial changes or malignant transformation.In a study by Silverman and Gorsky the overall malignanttransformation of OL was 17.5%, for the homogenousform only 6.6%, and for speckled OL 23.4%. Aspecial subtype of OL, PVL, was found to develop SCCin 70.3% of patients [322]. Compared with OL, OE hassignificantly worse biological behaviour, with 51% proceedingto malignant transformation [319].1.2.7.2 LarynxThe main task of the pathologist dealing with laryngealSILs is to separate non-risky or a minimally riskyfrom risky changes. Patients with benign hyperplasticlesions (simple and basal-parabasal hyperplasia) donot require such a close follow-up after excisional biopsiesas those with atypical hyperplasia and CIS, althoughelimination of known detrimental influencesis advised [125, 150]. Diagnosis of atypical hyperplasiain laryngeal lesions requires close follow-up and oftenrepeated histological assessment to detect any possiblepersistence or progression of the disease [125, 150, 178,181]. Patients with CIS may require more extensive surgicaltreatment or radiotherapy, although this is controversial[79, 181, 254, 299, 336].The histopathologic degree of severity of laryngealSILs is still used as the most reliable predictive factor[39, 125, 150, 178, 181, 239]. The frequency of subsequentmalignant alteration markedly increases fromsquamous (simple) and basal-parabasal (abnormal) hyperplasia(0.9%), compared with atypical hyperplasia(11 %) [150]. Barnes’s review of the literature shows thatthe risk of SCCs developing in mild, moderate and severelaryngeal dysplasia ranges from 5.5% to 22.5% and28.4% respectively [20].1.3 Invasive Squamous Cell Carcinoma1.3.1 Microinvasive SquamousCell CarcinomaICD-O:8076/3Microinvasive squamous cell carcinoma (SCC) is a SCCwith invasion beyond the epithelial basement membrane,extending into the superficial stroma. There is little consensusamong pathologists on the maximum depth ofinvasion in microinvasive SCCs, but it generally rangesfrom 0.5 mm [20] to 2 mm [77]. The depth of invasionmust be measured from the basement membrane of theadjacent (non-neoplastic) surface epithelium, because ofthe great variations in epithelial thickness.Microinvasive SCC is a biologically malignant lesioncapable of gaining access to lymphatic and blood vessels,which may result in metastases. However, metastasesare rare in microinvasive SCCs and the prognosisis excellent. Studies on SCCs of the floor of the mouthhave shown that there is little or even no metastatic potentialfor SCCs penetrating less than 2 mm beyond thebasement membrane, and a substantially higher risk ofmetastases in more deeply invasive SCCs at this site [74,77, 246]. The prognosis is also excellent in microinvasiveSCCs of the laryngeal glottis because of the poor lymphaticand vascular network in this location. Some authorshave therefore recommended more conservativetreatment of these lesions, such as endoscopic removal,with a careful follow-up [80, 308, 341].The reliable diagnosis of microinvasive SCC can onlybe made with certainty if the whole lesion is examined.It should not be made in small, tangentially cut biopsyspecimens.1.3.2 Conventional SquamousCell CarcinomaICD-O:8070/3Squamous cell carcinoma (SCC) is a malignant epithelialtumour with evidence of squamous differentiationsuch as intercellular bridges and keratin formation. Itoriginates from the surface squamous epithelium, orfrom ciliated respiratory epithelium that has undergonesquamous metaplasia [242].Squamous cell carcinoma of the head and neck is thesixth most prevalent cancer worldwide, accounting for5% of all new cancers, with a global annual incidenceof 500,000 [42]. The vast majority of SCCs are the conventionaltype of SCC, accounting for more than 90%of cases. The remaining cases belong to the variants ofSCC, which will be discussed later in this chapter.Squamous cell carcinoma of the head and neck occursmost frequently in the oral cavity and lip, in the