Abstract:

Neuroendocrine tumours of the bladder are less common than other histologic types (e.g., urothelial carcinoma, squamous cell carcinoma, adenocarcinoma), constituting 1% of malignant bladder cancers. Based on the “2016 World Health Organization Classification of Tumours of the Urinary System and Male Genital Organs”, neuroendocrine tumours are classified into four subtypes: small cell neuroendocrine carcinoma (SCNC), large cell neuroendocrine carcinoma (LCNC), well-differentiated neuroendocrine tumour (carcinoid tumour) and paraganglioma. SCNC is more common than other subtypes, and LCNC is exceedingly rare in the bladder. Although neuroendocrine tumours are not as common as neuroendocrine neoplasms of the lungs, the differential diagnosis of these tumours remains crucial and should be considered in uropathology. Neuroendocrine tumours of the bladder can present with distinctive morphology and grades, similar to their pulmonary counterparts. The knowledge of this diagnosis is critical to advance the uropathological field and accelerate drug development with inclusion, rather than exclusion, of patients with SCNC and other variants of neuroendocrine tumours of the bladder. Therefore, in this review, the bladder’s clinical and uropathological aspects of neuroendocrine tumours are reviewed. This classification provides a useful platform to discuss the aetiology, pathogenesis, clinical and pathological characteristics and treatment of the neuroendocrine tumours of the urinary bladder. The overall prognosis of urinary bladder neuroendocrine tumours is worse than urothelial carcinoma. Various advances are expected in the clinical characterisation, prognostication and treatment of neuroendocrine tumours of the bladder with the technologies developed in genetic and cellular investigations.

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