Noninvasive micropapillary urothelial carcinoma: a clinicopathologic study of 18 cases.

Noninvasive micropapillary urothelial carcinoma consists of slender tufts of urothelial carcinoma lacking fibrovascular cores analogous to ovarian papillary serous tumors of borderline malignancy. Eighteen noninvasive micropapillary urothelial carcinoma cases were identified from the Pathology Department of The Johns Hopkins Hospital (2000-2011). Patients lacked history of invasive urothelial carcinoma. Two patterns of noninvasive micropapillary urothelial carcinoma were identified: (1) as a variant of noninvasive high-grade papillary urothelial carcinoma (high-grade papillary urothelial carcinoma/micropapillary urothelial carcinoma) (n = 13 cases) and (2) as a variant of urothelial carcinoma in situ (carcinoma in situ/micropapillary urothelial carcinoma) (n = 5 cases with 2 of these patients also having high-grade papillary urothelial carcinoma/micropapillary urothelial carcinoma). Of 18 patients, 16 (88%) were male with a mean age of 71.8 years (range, 54-87 years). Of the 12 patients initially treated with surveillance, Bacillus-Calmette Guérin, or intravesical chemotherapy, 4 did not recur and were without evidence of disease at 6, 21, 24, and 39 months. Four patients experienced recurrences with 3 of them without evidence of disease at 36, 52, and 72 months and with the fourth whose last follow-up was at 84 months when recurrence occurred. One patient is alive at 11 months with disease, and 1 died of other causes at 1 month. Two patients progressed to pT2 and pT3 disease at 5 and 21 months, respectively. It is critical to differentiate and clearly specify in pathology reports whether micropapillary urothelial carcinoma is invasive or noninvasive because invasive micropapillary urothelial carcinoma is an aggressive disease with a high degree of understaging, whereas some cases of noninvasive micropapillary urothelial carcinoma are not necessarily associated with an adverse outcome.