Primary renal neuroendocrine with lymph nodal metastasis occurring in a horseshoe kidney: Report of a rare case with discussion on grading issues.

Primary renal well-differentiated neuroendocrine tumors (WDNETs) are uncommon tumors that differ in histological pattern, biological behavior, and response to treatment. There is a considerable correlation between WDNETs and congenital or acquired renal anomalies. We report a WDNET in a horseshoe kidney with lymph nodal metastasis in a 35-year-old male. This rare occurrence is discussed, especially the grading of these tumors and the value and vagaries of Mib-1 labeling index.