Bladder & urothelial tract
Neuroendocrine neoplasms
Well differentiated neuroendocrine tumor
Author: Turki Al-Hussain, M.D.
Last author update: 1 December 2014
Last staff update: 18 May 2021
Copyright: 2003-2025, PathologyOutlines.com, Inc.
PubMed Search: Bladder carcinoid tumor
Table of Contents
Definition / general | Epidemiology | Sites | Etiology | Clinical features | Case reports | Treatment | Gross description | Microscopic (histologic) description | Positive stains | Electron microscopy description | Differential diagnosisCite this page: Al-Hussain T. Well differentiated neuroendocrine tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bladdercarcinoid.html. Accessed January 18th, 2025.
Definition / general
- Rare low grade neuroendocrine carcinoma, similar to counterparts at other sites
- Formerly called carcinoid tumor
Epidemiology
- Usually ages 47-69 years
Sites
- Bladder neck and trigone
Etiology
- Thought to arise from isolated neuroendocrine cells located in the basal layer of the urothelium (Epstein: Bladder Biopsy Interpretation)
Clinical features
- Rare, < 50 cases described
- Patients present with hematuria
- No carcinoid syndrome
- Behavior is difficult to predict (Arch Pathol Lab Med 2006;130:1693); occasionally produces metastases and death
Case reports
- 54 year old woman with tumor arising beneath an inverted papilloma (Arch Pathol Lab Med 1994;118:666)
- 62 year old woman (Arch Pathol Lab Med 1992;116:1217)
- 68 year old man with calcitonin secreting tumor (BMC Cancer 2005 Jul 27;5:88)
Treatment
- Excision is usually curative, but behavior may not be predictable
Gross description
- Usually 1-2 cm
- Smooth-surfaced sessile polypoid nodules covered by urothelium
Microscopic (histologic) description
- Usually glandular growth pattern (Arch Pathol Lab Med 2003;127:e22)
- Other patterns include acinar, cribriform and trabecular
- Pure or mixed with carcinoma
Positive stains
Electron microscopy description
- Neuroendocrine differentiation
Differential diagnosis
- Inverted papilloma: lacks salt and pepper chromatin of carcinoid tumors; not invasive
- Metastasis: clinical history
- Nested variant of urothelial carcinoma: classic urothelial carcinoma usually present elsewhere; usually no well defined neuroendocrine features
- Paraganglioma: nests of tumor cells surrounded by S100+ sustentacular cells
- Direct invasion of carcinoid tumor from appendix: clinical history
