[Coordinated expression of cytokeratin 7 and 20 in transitional carcinoma of the bladder: diagnostic usefulness]

Cytokeratins are intermediate filament proteins which are part of the framework of eucariotic cells. A characteristic pattern of expression of cytokeratins has been described for each type of epithelium. This pattern is maintained during the process of malignancy and metastasis. Immunohistochemical analysis of cytokeratins 7 and 20 (Ck 7 and Ck 20) has been considered particularly useful for identifying the origin of carcinomas.

A total of 122 cases of transitional cell carcinoma of urinary bladder were studied immunohistochemically with monoclonal antibodies against Ck 7 and Ck 20. The peroxidase labelled-streptavidin biotin technique was performed. Cases were considered positive when at least 1% of tumoral cells were stained.

All cases investigated expressed Ck 7 whereas Ck 20 was positive in 75% of them. Reactivity for Ck 20 was always focal. No tumor was negative for Ck 7.

Ck 7+/Ck 20+ immunophenotype is highly characteristic of transitional cell carcinoma of urinary bladder, whereas Ck 7+/Ck 20- is less frequent. Immunohistochemical determination of these cytokeratins is useful for the diagnosis when tumors are poorly differentiated and for identifying the primary site of metastatic carcinomas.