膀胱臍尿管原發性神經內分泌腫瘤:案例報告

蔡仕傑¹、陳威任^{1, 2}、黃志賢^{1, 2}

¹臺北榮民總醫院泌尿部；²國立陽明交通大學醫學系泌尿學科及書田泌尿科學研究中心

Primary neuroendocrine tumor (NET) of urachus: a case report

Shi-Jie Tsai¹, Wei-Jen Chen ^{1, 2}, William J.S. Huang^{1, 2}

¹ Department of Urology, Taipei Veterans General Hospital,

²Department of Urology, College of Medicine and Shu-Tien Urological Science Research Center,

National Yang Ming Chiao Tung University, Taipei, Taiwan

Introduction

Neuroendocrine tumors are mainly distributed in lung and gastrointestinal tract. Primary neuroendocrine tumors of urinary bladder are exceedingly rare. Herein, we presented a rare case of neuroendocrine tumor of urachus origin.

Care presentation

This is a 44-year-old female patient without past history of systemic diseases. She had history of hysterectomy and salpingoopherectomy in 2011 due to endometriosis and chocolate cyst.

Patient had noticed gross hematuria for twice in October 2022, so she received physical checkup in November 2022. Urine routine revealed microscopic hematuria (RBC 50-99/HPF) without pyuria, and sonography revealed a 3.6cm midline anterior wall urinary bladder tumor. Then, she came to our urology clinic for help. Subsequent abdomen CT confirmed a 3cm tumor growth at bladder dome midline, with bladder whole layer involved, and cannot rule out tumor of urachal origin. TURBT was done on 2022/12/14, and the pathology reported neuroendocrine tumor (NET) with muscle layer invasion noted. After thorough discussion, she received partial cystectomy on 2022/12/21. The final pathology revealed neuroendocrine tumor, grade 2, which were positive for synaptophysin, INSM1, and SATB2. The tumor mainly located in the urachus and primary urachal NET is likely. The surgical margin was free. The post-operative recovery course was uneventful and Foley catheter was removed on 2023/01/03.

The patient was referred to oncologist for further evaluation. Reviewing her esophagogastroduodenoscopy and colonoscopy during physical checkup in 2022/11 showed no gastrointestinal tumor. Chest CT and abdomen MRI were then arranged and results were negative. There’s no other possible primary site of tumor was found to date. The patient is currently free of tumor recurrence four months after surgery.

Discussion

Neuroendocrine tumors of the urinary bladder are exceedingly rare and only comprise <1% of all bladder malignancies ^[1]. Owing to their low incidence and limited follow-up data in the literature, the clinical feature and diseases courses remain unclear nowadays.

The 2016 World Health Organization Classification of Tumors of Urinary System and Male Genital Organ classification system separates four subtypes of neuroendocrine tumors of the urinary bladder: small cell neuroendocrine carcinoma, large cell neuroendocrine carcinoma, well-differentiated neuroendocrine tumor (carcinoids), and paragangliomas ^[2]. The clinical behavior of carcinoids varies depending on their histopathology grade, which is determined by both the mitotic count and Ki-67. Low grade carcinoid tumors had excellent prognosis according to Chen et al. ^[3]. They reported 6 patients with primary carcinoids of urinary bladder or urethra. All of them were low grade and were treated with surgical resection. No disease recurrence or progression was noted after operation, including 3 patients with follow-up duration over 4 years. In contrast to carcinoids, urinary bladder small cell carcinoma usually behaves aggressively and associated with poor prognosis. Cheng et al. reported 5-year disease-specific survival as low as 16% ^[4]. Our patient was classified as well-differentiated NET, intermediate grade (grade 2). The prognosis of this urinary bladder NET subgroup was unclear, and no such case report can be searched in PubMed.

In conclusion, the optimal management of patients with urinary bladder NET has not been well established due to the rarity of cases. Since NET of bladder/urachus origin is rare, excluding primary NET in gastrointestinal tract is necessary. Localized bladder NET should be fully resected by curative-intent surgery in order to obtain enough specimen for correct pathological diagnosis.

References

1. Manunta A, Vincendeau S, Kiriakou G, Lobel B, Guillé F. Non-transitional cell bladder carcinomas. BJU Int. 2005;95(4):497-502.
2. Kouba E, Cheng L. Neuroendocrine Tumors of the Urinary Bladder According to the 2016 World Health Organization Classification: Molecular and Clinical Characteristics. Endocr Pathol. 2016;27(3):188-199.
3. Chen YB, Epstein JI. Primary carcinoid tumors of the urinary bladder and prostatic urethra: a clinicopathologic study of 6 cases. Am J Surg Pathol. 2011;35(3):442-446.
4. Cheng L, Pan CX, Yang XJ, et al. Small cell carcinoma of the urinary bladder: a clinicopathologic analysis of 64 patients. Cancer. 2004;101(5):957-962.