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[Neuroendocrine tumor in a horseshoe kidney: relative risk of association of two related entities].

OBJECTIVE
Primary renal neuroendocrine tumor (NET) is a very rare neoplasia with a higher frequency of appearance in horseshoe kidney (HK). From 1966, when Resnick published the first case, approximately 2 of each 10 new cases appear in kidneys with this malformation. From the diagnosis of a case of primary NET in a HK, we calculated the relative risk of their presentation as associated entities.


METHODS
63-year-old male with the incidental diagnosis of an 8 cm solid renal mass in the isthmus of a HK. At the time of diagnosis there were no signs of local-regional extension of the primary neoplasia neither metastasis. The patient underwent nephrectomy and pathologic study confirmed the diagnosis of NET. After a systematic review using multiple search platforms (Blackwell, Ovid, Proquest, PubMed, Science Direct, and Wiley) our case is No. 11 of NET in HK from a total of 57 renal NET.


RESULTS
Despite its very low frequency 19.3% of NET present in HK. Using 1/400 as the incidence of HK in general population, the calculated relative risk in HK is 77 times greater than that of a normal kidney


CONCLUSIONS
The relative risk of presentation of NET in HK is enormously superior than that of general population. This diagnosis must be suspected in patients with HK, mainly if the tumor is located in the renal isthmus. Due to its potentially aggressive clinical course and poor response to other therapies, measures for improvement of surgical treatment must be considered priority.