Pathology of the Head and Neck

20 N. Gale · N. Zidar1phoplasmacellular infiltration is usually present in thestroma at the base of the carcinoma, but is scarce withinthe papillae. If no stromal invasion is found, the lesionis called papillary atypical hyperplasia, PSCC in situ, ornon-invasive PSCC [328].1.3.5.3 Differential DiagnosisDifferential diagnosis includes squamous papilloma,VC, and SCC with an exophytic or fungating pattern.Papillomas and VCs share with PSCCs similar architecture,but PSCCs are differentiated from both VCs andpapillomas by the presence of atypia of the squamousepithelium covering the papillae. The differentiationbetween exophytic and papillary SCCs can be more difficultas the histologic criteria for the diagnosis of exophyticSCCs are not clearly defined [30, 355].1.3.5.4 Treatment and PrognosisTreatment of PSCCs is similar to that of conventionalSCCs. Patients with PSCCs are generally believed to havea better prognosis than those with conventional SCCs,although reports in the literature are controversial [343,355]. It appears that, because of a relatively small numberof cases published in the literature, PSCCs possiblyremain the least understood of the several variants ofSCC of the head and neck [30].1.3.6 Basaloid Squamous Cell CarcinomaICD-O:8083/3A basaloid squamous cell carcinoma ( BSCC) is a poorlydifferentiated SCC composed of basaloid cells and squamouscell carcinoma, characterised by an aggressive clinicalcourse. It was first described by Wain et al. in 1986[372]. It has a predilection for the upper aerodigestivetract, but also occurs in other locations such as the uterinecervix [140], oesophagus [202], lung [51], and anus [90].In the upper aerodigestive tract, BSCC shows a predilectionfor the hypopharynx (pyriform sinus), base ofthe tongue, and supraglottic larynx [195, 293]; it has alsobeen described in the oropharynx [195, 293], oral cavity[69, 72, 159] and trachea [277, 312]. The suggested precursorof the BSCC is a totipotent primitive cell locatedin the basal cell layer of the surface epithelium, or withinthe seromucinous glands [293, 372].1.3.6.1 AetiologyTobacco and alcohol use are strong risk factors for thedevelopment of BSCCs [19].1.3.6.2 Pathologic FeaturesMacroscopically, the tumour usually appears as a white,firm, poorly defined, exophytic, polypoid, and centrallyulcerated mass with peripheral submucosal infiltration[21].Microscopically, BSCCs are composed of small, closelypacked basaloid cells, with hyperchromatic nuclei withor without nucleoli, and scant cytoplasm (Fig. 1.17a).The tumour grows in a solid pattern with a lobular configuration,with a frequent peripheral palisading of nuclei.Large central necroses of the comedo type are frequent.Distinctive features of BSCCs that are not foundin conventional SCCs are small cystic spaces containingpara aminosalicylate (PAS)- and Alcian blue-positivematerial and focal stromal hyalinisation [19, 372].BSCCs are always associated with an SCC component,which can present either as an in situ or invasiveSCC. The invasive SCC is usually located superficially,and is typically well- to moderately differentiated.It may also present as focal squamous differentiationwithin the basaloid tumour islands. The transition betweenthe squamous cells and the basaloid cells is oftenabrupt (Fig. 1.17b), or there may be a narrow zone oftransition.If there is extensive ulceration, only dysplastic changesmay be identifiable in the intact surface epithelium[19, 21]. Rarely, BSCCs exhibit a malignant spindle cellcomponent [21, 250]. Metastases may demonstrate basaloidcarcinoma, squamous carcinoma, or both [21].By electron microscopy, desmosomes and tonofilamentswere demonstrated in basaloid cells and in squamouscells. There were no neurosecretory granules,myofilaments or secretory granules [154, 372].Immunohistochemically, BSCCs express keratin andepithelial membrane antigen, but the percentage of positivecells varies among different reports. It is advised touse a cocktail of keratin antibodies (i.e. CAM 5.2, AE-1-AE3) to avoid false-negative results [21]. Some casesexpress carcinoembryonic antigen and neuron-specificenolase [19, 195, 318], while expression of S-100 protein,vimentin and muscle-specific actin varied amongdifferent reports. Vimentin was negative in some studies[69, 195], while Barnes et al. [21] described positivestaining in the majority of basaloid cells, with a peculiarpattern of staining, forming a delicate perinuclear rim.Varying results have also been reported for S-100 immunoreactivity.Some authors described focal immunoreactivityin a few cases [19, 21], while others did not findany S-100-positive tumour cells [69, 195, 248]. However,most cases displayed numerous S-100-positive dendriticcells intermingled with the tumour cells [9, 21, 195,248]. BSCCs do not express chromogranin, synaptophysinand GFAP [19, 21, 195].