Urothelial and prostate carcinoma metastasizing to the same lymph node: a case report and review of the literature.

We report herein a case of a collision tumor composed of high-grade urothelial carcinoma and a Gleason grade 3+4 prostate adenocarcinoma metastasizing to the same lymph node. After the patient underwent cystoprostatectomy for known urothelial carcinoma, he was incidentally discovered to have a second primary prostate tumor. Lymph node examination revealed that one node appeared to have metastatic foci from both primary tumors. The presence of 2 tumor types colliding in the same lymph node was confirmed using immunohistochemical stains, including monoclonal carcinoembryonic antigen, prostate-specific antigen, prostatic acid phosphatase, cytokeratins 7 and 20, and CD57. We also stained both primary tumors with the same panel as an internal control. Although 2 similar collision tumors have been reported in the literature in the past, neither used a battery of immunohistochemical stains to definitively distinguish one tumor from the other. Herein, we review the literature on urothelial and prostate collision tumors and some of the special stains used to distinguish them.