The expression of CD44 glycoprotein adhesion molecules in basal cell carcinomas is related to growth pattern and invasiveness

Basal cell carcinomas (BCCs) of the skin exhibit a wide range of histological growth patterns as well as a highly variable rate of invasiveness. A large body of experimental and clinical studies supports a role for the CD44 glycoprotein family in the latter process. In the present study, we explored the distribution and the level of expression of pan-CD44, CD44v3, CD44v5 and CD44v6 in BCCs. The use of paraffin sections, combined with an antigen retrieval procedure, yielded far more detailed data than would have been possible with frozen sections. On average, the level of expression of the four CD44 isoforms studied appeared to differ relatively little. However, tumours or tumour areas consisting of thin tumour cell strands showed a significantly stronger expression of all four isoforms than those consisting of solid tumour cell groups. Furthermore, the highest CD44 expression was frequently observed in the smallest tumour cell strands in the tumour periphery. In these strands, the label seemed to be located not only at the tumour cell-tumour cell interface, as in other tumour areas, but also on the tumour cell surfaces facing the stroma. We are presently assessing the exact localization of CD44 at the cellular level by immunoelectron microscopy. In most cases, different growth patterns with significantly different levels of CD44 expression were found side by side within individual tumours. CD44 expression is therefore not a static tumour cell characteristic but is correlated with tumour architecture and tumour-stroma interaction.