A micropapillary variant of transitional cell carcinoma arising in the ureter

A 79-year-old woman was evaluated for a ureteral stricture related to laser ablation of a tumor 6 months earlier at another institution. A ureteroscop ic examination revealed an exophytic papillary tumor that was resected and examined histologically. The tumor was characterized by delicate papillae w ith thin stromal cores and numerous secondary micropapillae lined by small cuboidal to low columnar cells with uniform low-to-intermediate-grade nucle i, reminiscent of a serous borderline tumor of mullerian origin. The cell l inings were 1 to 4 layers thick; mitotic figures were easily identified. Th e underlying stroma appeared edematous and contained scattered chronic infl ammatory cells. No invasion was identified. After ascertaining that the pat ient had no known gynecologic neoplasm, the differential diagnoses consider ed included papillary nephrogenic adenoma, clear cell carcinoma, and the re cently described entity of micropapillary transitional cell carcinoma. Beca use of the striking resemblance to serous carcinoma and the presence of sig nificant mitotic activity, this case was felt to represent a case of microp apillary transitional cell carcinoma (World Health Organization grade 1 to 2) occurring in the ureter. To our knowledge, this tumor had some unique fe atures (no areas of grade 3 nuclei or invasion) that have not been reported in tumors occurring in the urinary bladder. The transitional cell nature o f the tumor cells was supported by the immunohistochemical staining pattern . The anatomic distribution of micropapillary transitional cell carcinoma i s now expanded to include the ureter, and this tumor should be considered i n the differential diagnosis for papillary lesions occurring in the ureter.