Utility of a dual immunostain cocktail comprising of p53 and CK20 to aid in the diagnosis of non-neoplastic and neoplastic bladder biopsies

p53+CK20 DIHC were examined in 38 reactive atypia, 10 dysplasia, 9 carcinoma in situ (CIS) and 7 invasive carcinoma (IC) cases. CK20 was evaluated according to distribution extent and degree of intensity whereas percentage of positive cells together with staining intensity was taken into account in the evaluation of p53.92% of reactive cases were either CK20(-) or (+) only in the upper 1/3 urothelium. In dysplastic cases CK20 staining distribution was as follows: 60% in 2/3 of the urothelium, 30% full thickness, 10% in the upper 1/3 urothelium. Among CIS cases, 89% had full thickness CK20 positivity, of which 62% were p53(+). 71% of IC cases exhibited strong and full thickness dual staining.This is the first study in the literature to use DIHC of p53+CK20 in distinction of non-neoplastic and neoplastic bladder lesions. Dual staining by p53+CK20 cocktail allows for histologic correlation and diminishes the risk of losing the area of interest in limited biopsy specimens.Urothelial carcinoma is the 7th most common cancer worldwide with 260,000 new cases in men and 76,000 cases in women per year [1]. Furthermore, it is the 4th leading cause of cancer in American men with 14,100 deaths per year in the US [2].2004 World Health Organization/International Society of Urological Pathology (WHO/ISUP) consensus committee classifies flat urothelial lesions with atypia as reactive urothelial atypia (RUA), atypia of unknown significance (AUS), urothelial dysplasia (UD) and carcinoma in situ (CIS) [1,3]. UD is defined by "appreciable loss of polarity with nuclear rounding and crowding and cytologic atypia that is not severe enough to merit a diagnosis of CIS." whereas AUS is a descriptive category for cases in which dysplasia cannot be ruled out for sure, because of a degree of atypia that is discordant with the extent of inflammation [1]. Both UD and CIS are precursor lesions of invasive carcinoma and their presence is associated with a high risk of progression and recurrence [3-5