Clinicopathological features and prognosis of small cell carcinoma of the urinary bladder

This study aimed to investigate the clinicopathological features and prognosis of small cell carcinoma of the urinary bladder (SCCUB).

Clinicopathological data and prognosis of 24 patients with primary SCCUB treated at the Affiliated Hospital of Qingdao University (from January 2016 to December 2021) were retrospectively collected and compared with 335 patients with primary high-grade urothelial carcinoma (HG-UC) during the same period. The study endpoints were disease-free survival (DFS) and overall survival (OS).

Of the 24 patients with SCCUB, 19 were male and five were female. Eight (33%) cases were pure SCCUB (pSCCUB). Sixteen (67%) cases were mixed SCCUB (mSCCUB), all of which were mixed with urothelial carcinoma. All patients underwent surgery and 13 (76%, 13/17; seven patients were lost to follow-up) patients received postoperative adjuvant chemotherapy. We found no significant difference in clinicopathological features between pSCCUB and mSCCUB. However, compared to HG-UC, SCCUB had higher lymph node metastasis (p=0.014), more lymphovascular invasion (p=0.024), higher Ki-67 expression (p<0.001), and more disease progression events (p=0.001). Median DFS and OS for SCCUB were 22 months and 38 months, respectively. The Kaplan-Meier survival curve showed that the pathological type or surgical type did not affect DFS or OS of SCCUB. However, SCCUB patients had worse DFS and OS than HG-UC patients (both p<0.05). The multivariate Cox analysis showed that the tumor size (hazard ratio 1.44, 95% CI 1.96-2.15, p=0.048) was an independent factor affecting DFS of SCCUB patients.

Compared with the common HG-UC, SCCUB is rare with specific clinicopathological features and a worse prognosis.