Micropapillary carcinoma of the urothelial tract. A clinicopathologic study of 38 cases.

Micropapillary carcinoma (MPC) of the bladder is a rare and aggressive variant of bladder carcinoma. The goals of this study are to investigate whether this variant of bladder carcinoma represents a more aggressive disease than conventional urothelial carcinoma (CUC) and to determine the incidence of MPC in our country. A total of 630 urothelial carcinomas diagnosed from 1997 to 2003 at the Department of Pathology, Oncology Hospital, in Mexico City were analyzed to identify MPC. Thirty-eight patients were found to have this diagnosis and along with a group of 76 patients diagnosed with CUC serve as the basis for this study. In 37 patients with MPC, the lesions were located in the bladder, and in 1 patient in the ureter. The mean patients' age at diagnosis was 68 years, and the male-female ratio was 37:1. The initial stage at presentation was high in most of the patients: Three patients had stage T1, 8 had stage T2, 18 had stage T3, and 9 had stage T4. The disease-specific survival rate for patients with MPC at 3.1 years was 39.5% (95% confidence interval [CI], 2.7%-3.4%) whereas for patient with CUC was 55.3% (95% CI, 3.9%-4.4%). Patients with a micropapillary component of more than 50% had a relative mortality risk of 2.4 (1.3-4.2), whereas patients with less than 50% of MPC did not have a significantly increased mortality risk (RR, 1.8; 0.5-6.0). In summary, in this study, MPC was far more aggressive clinically than CUC. In Mexico, the incidence of 6% of MPC in relation to CUC and the male-female ratio of 37.1 for MPC are much higher than reported in the literature.