Large renal lymphoma in a patient with horseshoe kidney: A case report.

Horseshoe kidney (HSK) is the most common renal fusion anomaly. It frequently consists of kidney fusion in the lower pole across the midline and occurs during embryogenesis. The incidence of malignancies in HSKs can be 3-4 times higher than that in normal kidneys. A 69-year-old man with a voluminous right kidney neoplasm in HSK and a single omolateral axillary lymphadenopathy underwent complete excision of right axillary lymphadenopathy and ultrasound-guided percutaneous biopsy of the right kidney expansive lesion. The diagnosis of non-Hodgkin's B cell lymphoma both in HSK and right axilla was made. We report this case to raise awareness among physicians regarding the importance of a correct clinical evaluation and diagnostic workup so as to avoid surgery, which is not easy and without complications, in patients with this kidney anomaly. Primary renal lymphoma should also be included among possible neoplasms of HSK. Renal biopsy should always be recommended in cases where atypical findings are obtained from imaging techniques and when its outcome can impact clinical decision-making. In the present case, biopsy was performed, and thus, nephrectomy was avoided and specific medical therapy was quickly started.