Well Differentiated Neuroendocrine Tumors of Lower Urinary Tract: Biologic Behavior of a Rare Entity

The spectrum of neuroendocrine (NE) tumors in the genitourinary tract ranges from the aggressive large and small cell carcinomas to the often benign paraganglioma and well differentiated neuroendocrine tumor (WD-NET). At least 15 pure lower urinary tract (LUT) WD-NETs have been described. Due to the rarity of WD-NET in LUT and the limited number of reported cases, a better definition of their biologic long term behavior is warranted. Herein, we aim to describe 10 new cases of WD-NET arising in LUT and expand on follow-up findings. Ten consultations cases were identified and included 6 males and 4 females who ranged from 45 to 73 years of age. Seven cases arose in bladder with one located in bladder neck, 1 in prostatic urethra, 1 in female urethra and 1 in left ureteral orifice. All lesions were confined to the lamina propria and tumor architecture was pseudoglandular in all cases. Associated cystitis cystica et glandularis (CCCG) was identified in 5 cases; urothelial papilloma and florid Von Brunn's nests in 2 additional cases. IHC stains for synaptophysin and chromogranin were diffusely positive in 9 cases and focal in 1 and Ki-67 proliferation index was 5% or less in all tumors. Follow-up ranged from 37 to 137 months (mean 82; median 77) and there was no evidence of residual disease or recurrence in any of the 10 patients during the follow-up period.