Expression of cytokeratin 20 redefines urothelial papillomas of the bladder

Expression of cytokeratin 20 redefines urothelial papillomas of the bladder

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Introduction The nomenclature of urothelial tumours is unique in that the WHO classification 1 recognises non-invasive urothelial carcinomas, despite the fact that it is the invasive behaviour of tumours that leads to local and distant spread, which is the hallmark of the cancer. The definition and diagnosis of urothelial papillomas as benign tumours that do not require further intervention is controversial, 2–5 and in practice is seldom used. The term carcinoma is preferentially used because it triggers a follow-up protocol of regular cystoscopies aimed at the prevention or early identification of invasive disease, which occurs in a small proportion of patients. 6 Because it is difficult to reliably identify this small group of patients by means of clinical criteria or standard morphology, all patients are given a diagnosis of cancer. This practice has profound practical and psychological effects for the patient and may also affect cancer statistics. In the Netherlands between 1975 and 1989, there was an increase in age-adjusted incidence of bladder cancer per 100 000 person-years from 25·9 to 40·7 in men and from 3·1 to 8·5 in women. This increase has been attributed to the inclusion of non-invasive tumours after the adoption of the WHO classification and changes in reporting procedures. 7 If standard morphology is a poor predictor of outcome in individual patients, it is important to explore more sensitive ways to classify tumours. In normal urothelium, the expression of intermediate filament cytokeratin 20 (CK20) is related to differentiation and is limited to superficial and occasional intermediate cells (figure 1). Abnormalities of urothelial differentiation are accompanied by loss of this restriction, so that expression of CK20 is seen in all cell layers (figure 1). 8 We postulated that if a papillary non-invasive tumour retained a normal pattern of CK20 expression, it would fulfil the criteria for the diagnosis of a benign tumour, because of the evidence of normal urothelial organisation and the absence of invasion. If this normal pattern of expression could be associated with low rates of recurrence and no progression, we could then identify a clinically meaningful category of tumours. We have previously identified a subgroup of patients with non-invasive urothelial tumours with a normal pattern of CK20 expression who had no recurrence during 5 years in a retrospective study. 9 The study we report aimed to confirm this finding prospectively by an investigation of all new non-invasive tumours with the CK20 marker. Summary Background Most non-invasive urothelial tumours of the bladder are diagnosed as papillary carcinomas in accordance with the WHO classification and because the identification of papillomas is difficult by routine histology; some patients are therefore misdiagnosed. This practice is associated with psychological morbidity for the patient and may also skew cancer statistics. Cytokeratin 20 (CK20) is a sensitive marker of urothelial differentiation. We
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This note was uploaded on 02/22/2011 for the course HTEC 50 taught by Professor Hassel,patricia during the Spring '11 term at DeAnza College.

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Expression of cytokeratin 20 redefines urothelial papillomas of the bladder

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