Micropapillary Variant of Urothelial Carcinoma in the Upper Urinary Tract: A Clinicopathologic Study of 11 Cases

Abstract

Abstract Context.—Micropapillary urothelial carcinoma (MPUC) is a rare variant of urothelial carcinoma. Most studies of MPUC have focused on the urinary bladder, but MPUC of the upper urinary tract remains to be investigated. Objective.—To investigate the pathologic features and clinical significance of MPUC in the upper urinary tract. Design.—We searched the pathology files at our institution and identified 11 cases of MPUC of the upper urinary tract. The histology slides were reviewed, and the clinical information was obtained by review of medical charts. Results.—The average age of the patients was 64.2 years (range, 22–76 years). The tumors were located in the renal pelvis (n = 5), ureter (n = 4), and ureteropelvic junction (n = 2). In all cases, MPUC accounted for an average of 45% (range, 10%–80%) of the tumor and was associated with conventional urothelial carcinoma. Lymphovascular invasion was present in all cases, and metastasis to lymph node was present in 4 of 5 patients whose lymph nodes were dissected. Two patients presented with pT2 disease, and both were alive without evidence of disease at 85 and 119 months after surgery. The other 9 patients presented with pT3 or pT4 disease: 4 of them died of disease at an average of 18 months; 4 surviving patients developed distant metastases; and 1 surviving patient with limited follow-up (6 months) showed no evidence of disease. Conclusions.—Micropapillary urothelial carcinoma of the upper urinary tract often presents at an advanced stage with lymphovascular invasion and distant metastasis. The presence of MPUC, even focal, indicates a poor clinical course.