Plasmacytoid urothelial carcinoma of renal pelvis with positive zinc finger E–box–binding homeobox 1: a case report

BACKGROUND: The tumor transformation mechanism of a plasmacytoid urothelial carcinoma remains unexplained. We describe the case of a plasmacytoid urothelial carcinoma of the renal pelvis in which the expression of zinc finger E–box–binding homeobox 1 (ZEB1), a key nuclear transcription factor in an epithelial–mesenchymal transition, is involved in tumor transformation. CASE PRESENTATION: The patient had a left nephrectomy with the clinical diagnosis of left pelvic renal cancer. The resected specimen showed that the tumor surface comprised a noninvasive papillary urothelial carcinoma with the carcinoma in situ, and the invasive area comprised a plasmacytoid urothelial carcinoma characterized by the presence of single dyscohesive malignant cells that resembled plasma cells in a loose myxoid stroma. The noninvasive urothelial carcinoma was positive for cytokeratin and E–cadherin, and negative for vimentin and ZEB1. In contrast, the invasive plasmacytoid urothelial carcinoma was positive for cytokeratin and also vimentin and ZEB1, and negative for E–cadherin. Additionally, this component was immunoreactive for CD138 and CD38 that are immunohistochemical markers for plasma cells. CONCLUSION: We suggest that ZEB1 is involved in the plasmacytoid transformation by repressing the E–cadherin in a plasmacytoid urothelial carcinoma.