CYTOKERATIN-20 AS AN OBJECTIVE MARKER OF UROTHELIAL DYSPLASIA

Objective To investigate the dysregulation of cytokeratin 20 (CK20) ex pression in urothelial dysplasia and its potential as a diagnostic aid . Patients and methods Twenty-two patients were selected on the basis that they had undergone one or more biopsies showing dysplasia before the development of a transitional cell carcinoma (TCC); 15 of these pa tients also had a prior history of TCC. The dysplasia was classified a s mild in 12 moderate in 14 or severe dysplasia/carcinoma in situ in 1 0 patients, ensuring that a spectrum of morphological appearances was represented. Control biopsies were obtained from seven children underg oing bladder reconstructions and 23 patients with recurrent urinary tr act infections, haematuria or functional bladder symptoms, but no hist ory of TCC. Results The expression of CK20 was restricted to superfici al 'umbrella' cells and occasional intermediate cells in the control b iopsies, even in the presence of severe inflammation. In 31 of the 36 cases of dysplasia. complete loss of restriction was seen at least foc ally, with positive expression in all layers of the urothelium. Conclu sion The abnormal expression of CK20 is a reliable, positive marker of urothelial dysplasia in the urinary bladder. Immunostaining for CK20 is therefore a useful adjunct to morphology in the diagnosis of dyspla sia, of particular value in the distinction from reactive states where diagnostic difficulties are greatest.