Late recurrence after radical nephrectomy for renal cell carcinoma in a patient with horseshoe kidney: a case report.

INTRODUCTION: Horseshoe kidney (HSK) is the most common renal fusion malformation. Renal cell carcinoma (RCC) is the most prevalent malignancy reported in this anomaly. CASE PRESENTATION: We present the case of a 61-year-old man with multiple recurrences of RCC in the context of HSK and pancreatic metastasis during a 15-year follow-up. He was initially diagnosed in January 2011 with a renal mass in the left lower pole of the HSK and underwent a left partial nephrectomy, which confirmed RCC. Recurrences followed, necessitating another partial nephrectomy in April 2014 and a left radical nephrectomy 3 months later. In January 2025, he was found to have a mass in the upper pole of the right kidney and a mass in the pancreatic tail, both confirmed as RCC metastases. The patient received oncologic treatment after a multidisciplinary consultation. DISCUSSION: This case emphasizes the importance of comprehensive interrogation in patients with a history of RCC due to the potential for asymptomatic recurrence or metastasis. CONCLUSION: HSK affects the therapeutic management of concurrent pathologies, such as malignancies. A history of RCC necessitates regular follow-up to evaluate for recurrence, regardless of the number of years since nephrectomy.