A synchronous occurrence of urothelial carcinoma with abundant myxoid stroma and inverted papilloma of the urinary bladder.

Abundant myxoid stroma rarely occurs in urothelial carcinomas, and may cause diagnostic challenges when cells with eosinophilic cytoplasm forming nests and cords in a myxoid background are seen, particularly in the absence of typical carcinomatous appearance. Microscopic examination of transurethral resection specimen of a 71-year-old male patient revealed non-cohesive oval or elongated tumor cells with eosinophilic cytoplasm arranged in cord-like filigree pattern in an abundant myxoid stroma. Immunohistochemically the tumor was positive for cytokeratin 7, cytokeratin 20, and 34BE12. About 90 to 100% nuclear staining was observed with p63, p53, and Ki-67. A second neoplasm with a flat overlying urothelial epithelium and a complete inverted cellular growth pattern was also noted. The neoplasm exhibited less than 2% and 10% nuclear staining with Ki-67 and p53, respectively. Considering histological, histochemical, and immunohistochemical findings, a diagnosis of synchronous urothelial carcinoma with abundant myxoid stroma and inverted papilloma was made.