Primary testicular neuroendocrine tumor with retroperitoneal lymph nodes metastasis: a case report.

Testicular neuroendocrine tumor (TNET) is an exceedingly rare malignancy with variable biological behavior. We report a 49-year-old male presenting with painless right testicular enlargement. Primary TNET (G1) was diagnosed after extensive pathological sampling and the clinical exclusion of extra-testicular primary sites via contrast-enhanced CT. Following radical orchiectomy, the patient underwent laparoscopic retroperitoneal lymph node dissection (RPLND), which confirmed metastatic involvement (7/13 nodes). Although severe intraoperative adhesions to the great vessels were encountered, a thorough dissection was performed, and postoperative imaging showed no measurable macroscopic residual disease, consistent with a clinical R0 resection. Based on a multidisciplinary team (MDT) assessment of the high risk for subclinical microscopic residuals, adjuvant therapy with surufatinib, a multi-targeted TKI, was initiated. A complete response (CR) was achieved eight months postoperatively, defined by the disappearance of all target lesions on follow-up contrast-enhanced CT according to RECIST 1.1 criteria. The patient remains disease-free at the one-year follow-up, suggesting that targeted therapy may be a promising and effective option for metastatic G1 TNET following surgical debulking.