Parham Parvazinia¹, Tracey Lu¹

¹ Capital pathology, Canberra, Australia

Well-differentiated neuroendocrine tumours (WDNETs) of the urinary bladder are indolent and exceedingly rare neoplasms, often associated with reactive urothelial lesions such as cystitis cystica et glandularis. We report a case of bladder WDNET associated with cystitis cystica.

 

A 66-year-old man was found to have an incidental lesion in the bladder trigone. Histopathological examination revealed a tumour with acinar and cribriform architecture, located beneath an area of cystitis cystica. The tumour cells showed monomorphic nuclei with speckled chromatin, and eosinophilic cytoplasm with occasional granules. No mitotic activity or necrosis was identified, and the tumour cells were positive for neuroendocrine markers, confirming the diagnosis of WDNET.

 

Bladder WDNETs are typically small and confined to the lamina propria, predominantly occurring in middle-aged to elderly men. Most reported cases have shown no adverse outcomes on long-term follow-up. It has been suggested that these tumours may arise from an increased number of neuroendocrine cells in associated cystitis cystica or glandularis, as observed in this case.^1-3

 

Accurate diagnosis of WDNETs is essential, as their morphology can resemble certain aggressive neoplasms in the bladder, such as invasive urothelial carcinoma (tubular and microcystic subtypes), potentially leading to unnecessary treatment interventions.³

                                                                                          

1.     Krijger RR, Ro JY, Rubin MA, et al. Well-differentiated neuroendocrine tumour. In: WHO Classification of Tumours Editorial Board. World Health Organization Classification of Urinary and Male Genital Tumours. 5^th ed. Lyon: IARC, 2022. Cited 16 Sep 2024. https://tumourclassification.iarc.who.int/chaptercontent/36/58

2.     Marletta S, Martignoni G, Ghimenton C, et al. Well-differentiated neuroendocrine tumour of the urinary bladder expressing GATA3. Virchows Arch 2022; 482: 783-8.

3.     Chen YB, Epstein JI. Primary carcinoid tumours of urinary bladder and prostatic urethra: a clinicopathologic study of 6 cases. Am J Surg Pathol 2011; 35: 442-6.

 

 

My original contribution to this case report includes identifying and selecting the case, conducting a detailed histopathological examination, correlating the clinical and pathological findings, formulating the differential diagnoses, performing the literature review and drafting the case report in collaboration with the co-author.