Cytokeratin 14 as a marker of squamous differentiation in transitional cell carcinomas.

The presence of squamous differentiation in transitional cell carcinomas has been variably related to prognosis and response to radiotherapy. This study sought to establish whether cytokeratin (CK) 14, normally expressed in the basal cells of squamous epithelium, could be used as a reliable marker of the emergence of a squamous phenotype in transitional cell carcinomas. In a series of 42 tumours, CK14 was expressed in areas of squamous morphology, whereas CK20 identified continuing urothelial differentiation. Furthermore, focal positivity for CK14 was present in a proportion of tumours with no morphological evidence of squamous differentiation, suggesting that it is a more sensitive marker of phenotypic switch. Investigation of CK subtypes may be more powerful than morphology alone in clinical studies of transitional cell carcinomas as CK expression profiles have been related to treatment response in other tumour types.