The nested variant of urothelial carcinoma: a rare but important bladder neoplasm with aggressive behavior. Three case reports and a review of the literature.

OBJECTIVE: To describe our experience with the nested variant of urothelial carcinoma (UC-NV) of the bladder, by characterization of the clinical picture and the prognostic implications of this rare form of bladder neoplasm.
MATERIALS AND METHODS: Three cases of UC-NV of the bladder treated in our institutions were revised and data compared with previously published case-reports.
RESULTS: Three patients presented with advanced muscle-invasive UC-NV, of which two had lymph node metastasis at cystoprostatectomy. The histopathology in the latter two cases showed the same picture in the lymph node metastasis as in the primary tumor with nests of tumor cells with mild-moderate atypia. In all three cases the tumor involved a ureteric orifice or the bladder neck.
CONCLUSION: UC-NV is a rare but important histopathologic entity. It has a poor prognosis. At early stage, tumors might be difficult to differentiate from benign conditions and awareness of the condition is of outermost importance.