Glandular neoplasms involving the urinary bladder carry a challenging differential diagnosis including primary and secondary processes. We investigated the potential diagnostic utility of cadherin-17 and GATA3 in 25 primary adenocarcinomas of the urinary bladder, as compared with other commonly used markers including β-catenin and p63. Urothelial carcinoma with glandular differentiation (11), colorectal adenocarcinoma secondarily involving the bladder (25), and primary colorectal adenocarcinoma (22) were also analyzed and the results were compared using a Fisher exact test. Cadherin-17 was expressed in 23/25 primary bladder adenocarcinomas (92%), 23/25 colorectal adenocarcinomas involving the bladder (92%), 21/22 primary colorectal adenocarcinomas (95%) and entirely negative (0/11) in both components of urothelial carcinoma with glandular differentiation (P<0.001). In urothelial carcinoma with glandular differentiation, positive nuclear staining for GATA3 was evident in the urothelial component for 18% (2/11) and the glandular component for 9% (1/11) with additional tumors showing only cytoplasmic staining. Nuclear reactivity for GATA3 was not present in primary bladder adenocarcinoma and primary/secondary colorectal adenocarcinoma (P<0.05). Positive nuclear and cytoplasmic immunostaining for β-catenin was evident in 21/22 primary colorectal adenocarcinomas (95%) and 23/25 cases of secondary involvement by colorectal adenocarcinoma (92%). In contrast, positive membranous and cytoplasmic staining for β-catenin was observed in 23/25 primary bladder adenocarcinomas (92%) and 11/11 urothelial carcinomas with glandular differentiation (100%, P<0.001). p63 was expressed only in the urothelial component of urothelial carcinoma with glandular differentiation and not in the glandular component (P<0.001). In summary, cadherin-17 is a relatively specific and sensitive marker for primary adenocarcinoma of the urinary bladder, distinguishing it from urothelial carcinoma with glandular differentiation. However, it does not distinguish primary bladder adenocarcinoma from secondary involvement by colorectal adenocarcinoma. The pattern of reactivity for β-catenin remains the most useful marker for distinguishing these two tumors.