Lectin histochemistry of normal and neoplastic nasopharyngeal epithelium

The cell surface carbohydrate profile of formalin-fixed paraffin-embedded tissue sections of normal and neoplastic epithelium was evaluated using 9 plant lectins. Three lectins, namely Con A, RCA and WGA, showed a similar pattern and staining intensity from normal epithelium to metaplastic squamous epithelium and nasopharyngeal intraepithelial neoplasia (NPIN). However, a decrease in staining reactivity was observed in undifferentiated nasopharyngeal carcinoma. Significant differences in intensity and distribution were seen in UEA and cryptic PNA residue (after neuraminidase pretreatment) from normal nasopharyngeal epithelium to NPIN. Infiltrative undifferentiated carcinomas showed a heterogenous lectin binding pattern and altered intensity of lectin binding in one case of DBA and three cases of PNA (no neuraminidase pretreatment), suggesting a variation in expression of carbohydrate by tumour cells. These results indicate that neoplasia in nasopharyngeal epithelium is associated with alterations in terminal sialic acid, -Fucose residues and -Gal-D-GalNac residues present in the outer parts of glycoconjugates. SBA, VVL and BSL failed to stain any types of epithelia. Desialylation of tissues by preincubation with neuraminidase did not expose DBA, SBA, VVL and BSL binding sites. These findings may be used as a baseline for evaluation of lectin binding in preinvasive and invasive lesions of the nasopharynx.