Primary renal neuroendocrine tumor (NET) is an extremely rare disease with fewer than 100 reported cases to date. Among them, only three involved the renal pelvis, to our knowledge. Here, we report another rare case of primary NET in the renal pelvis of a 33-year-old man. Initial computed tomography (CT) scanning of the abdomen and pelvis revealed a necrotic mass with peritumoral infiltration at the left renal pelvis and ureteropelvic junction causing urinary tract obstruction. A follow-up CT scan revealed an intratumoral hemorrhage. The patient then underwent nephrectomy. The results of a subsequent histopathological examination were consistent with a well-differentiated NET. No lymph nodes or paraganglia were found within the tumor, and further imaging revealed no other primary or metastatic lesions. Therefore, the patient was diagnosed with primary NET in the renal pelvis. We discuss this rare case and briefly review the current NET literature.
