PRIMARY METASTATIC RENAL CARCINOID IN HORSESHOE KIDNEY

Background: Primary carcinoid is a neuroendocrine tumour of low degree of malignancy. It is very common in the gastrointestinal tract, lungs and in other body regions. Renal carcinoid, frequently associated with horseshoe kidney, is very rare (in the literature only 56 cases are described). The natural history of the disease has better prognosis when associated with horseshoe kidney than in normo-functional ones. The history of a patient suffering from a renal carcinoid in a horseshoe kidney, who had liver metastasis after six years from the first surgery, was reviewed. Case Report: A 56-year-old male patient, who underwent abdomino-pelvic ultrasound and total body CT scan, showed a horseshoe kidney and a bulky solid mass of 6×6 cm at the lower pole of right kidney. The patient underwent partial nephrectomy with resection of the lower half of the affected kidney and the isthmus; the excision margin was 2 cm of normal renal parenchyma on either side of the mass. Microscopic examination of the lesion gives evidence of renal carcinoid. The immunohistochemical test showed that the tumour tissue was strongly positive for cytokeratin, chromogranin-A and synaptophysin. After a follow-up of 24 months, he was still negative for recurrence or distant metastasis. In March 2008, the patient had the first metastasis of the liver. He underwent a second surgery to remove the lesion. At the microscopic evaluation the diagnosis of welldifferentiated neuroendocrine carcinoma was confirmed. The later instrumental tests demonstrated presence of several metastatic lymph node recurrences. Results: Primary carcinoid of the kidney has a slow clinical course. Young adults (+/- 50 years old) without distinction of sex are most affected. On average, 50% of patients report flank/abdominal pain and/or hematuria and 7% present a carcinoid syndrome at the time of diagnosis; the remaining cases are asymptomatic. Conclusion: Renal carcinoid has better prognosis in the horseshoe kidney than in kidney with normal compliance. Recurrences are not excluded and the treatment of choice remains the full or partial nephrectomy.