Pathology of the Head and Neck

Lesions of Squamous Epithelium Chapter 1 21Fig. 1.17. Basaloid squamous cell carcinoma.a Closely packed basaloid cells with hyperchromaticnuclei and scant cytoplasm,with focal peripheral palisading of nuclei.b Abrupt transition between squamous andbasaloid cells. c Focal squamous differentiationin adenoid cystic carcinoma. Courtesyof Dr. Pieter J. Slootwegabc1.3.6.3 Differential DiagnosisDifferential diagnosis includes neuroendocrine carcinoma,adenoid cystic carcinoma, adenocarcinoma andadenosquamous carcinoma.Neuroendocrine carcinomas express various neuroendocrinemarkers that help to distinguish neuroendocrinecarcinomas from BSCCs. However, as 60–75%of cases of BSCC have been reported to express neurone-specificenolase [19, 65, 318] the application of otherneuroendocrine markers, including chromogranin,CD56, and synaptophysin, is advised [19, 65].Adenoid cystic carcinomas, especially the solid variant,may resemble BSCCs but adenoid cystic carcinomasrarely show squamous differentiation (Fig. 1.17C). Immunohistochemistrymay also be helpful: tumour cellsin adenoid cystic carcinomas express S-100 protein andvimentin, while tumour cells in BSCCs usually do notexpress either of the two markers [21, 195].Adenocarcinomas and adenosquamous carcinomascan be distinguished from BSCCs by the presenceof gland formation and mucin secretion within the tumourcells.1.3.6.4 Treatment and PrognosisA BSCC is an aggressive, rapidly growing tumour characterisedby an advanced stage at the time of diagnosis anda poor prognosis. Metastases to the regional lymph nodeshave been reported in two-thirds of patients [19, 195, 277,293], and distant metastases involving lungs, bone, skinand brain in 37–50% of patients [19, 195, 293].It is generally believed that BSCCs are more aggressivethan conventional SCCs [103, 108, 195, 372, 377].However, some studies indicate that BSCCs exhibit behavioursimilar to that of high-grade conventional SCCsof the head and neck [19, 134, 222, 376].The treatment of choice is radical surgical excisionand, because of early regional lymph node and distantvisceral metastases, radical neck dissection and supplementaryradio- and chemotherapy [21, 372, 375].