Colonic adenocarcinoma metastatic to the urinary tract versus primary tumors of the urinary tract with glandular differentiation: a report of 7 cases and investigation using a limited immunohistochemical panel.

To determine whether a limited immunohistochemical panel can help differentiate metastatic colonic adenocarcinoma from primary enteric-type adenocarcinoma of the urinary tract and urothelial (transitional cell) carcinoma with glandular differentiation, which appear morphologically similar but most often necessitate different treatment protocols. We examined lower urinary tract tumors (5 urinary bladder, 2 urethral) from 7 patients with a history of colonic adenocarcinoma. The differential diagnoses in these cases included metastatic colonic adenocarcinoma, primary enteric-type adenocarcinoma of the urinary tract, and urothelial carcinoma with glandular differentiation. An immunohistochemical panel consisting of cytokeratin 7 (CK-7), cytokeratin 20 (CK-20), and villin was evaluated in all cases. Four primary enteric-type adenocarcinomas of the urinary tract and 5 conventional urothelial carcinomas were also studied to compare morphologic features and immunohistochemical staining patterns. Of the 7 cases, 6 were determined to be metastatic colonic adenocarcinoma and 1 was diagnosed as a primary urothelial carcinoma with glandular differentiation. All 6 metastatic colonic adenocarcinomas, 6 of the 7 primary colonic adenocarcinomas, and all 4 primary enteric-type adenocarcinomas of the urinary tract were CK-20 positive (1 was CK-20 negative), villin positive, and CK-7 negative. The single urothelial carcinoma with glandular differentiation and all 5 control cases of urothelial carcinoma were CK-7 and CK-20 positive, and villin negative. We conclude that (1) villin is expressed in primary enteric-type adenocarcinoma of the urinary tract; (2) in difficult cases, urothelial carcinoma with glandular differentiation can be distinguished from colonic adenocarcinoma because the former is CK-7 positive, CK-20 positive, and villin negative, whereas the latter is CK-20 positive, villin positive, and CK-7 negative; (3) clinical information is essential when evaluating lower urinary tract tumors that are clinically and morphologically similar to enteric-type adenocarcinoma of the urinary tract; and (4) the similar immunohistochemical profiles of metastatic colonic adenocarcinoma and primary enteric-type adenocarcinoma of the urinary tract may be in keeping with the hypothesis that the latter arise from intestinal metaplasia.