Primary benign vascular tumors and tumorlike lesions of the kidney: a clinicopathologic analysis of 15 cases.

Primary benign vascular lesions of the kidney are uncommonly encountered in routine surgical pathology practice. They can, however, mimic malignancy or be an incidental finding adjacent to a malignancy. Fifteen specimens harboring 16 primary benign renal lymphatic/vascular lesions were identified from our files from 1999 to 2011 and subjected to a detailed pathologic evaluation and clinicopathologic correlation. Clinical and demographic data were available for all the 15 cases. There were ten males and five female patients with age range of 33-74 years (mean 54 years). Lesions ranged from 0.5 cm to 40 cm (average, 6.6 cm). There were six arteriovenous malformations (AVMs), four hemangiomas, three anastomosing hemangiomas, two lymphangiomas, and one solid intravascular papillary endothelial hyperplasia (IPEH). Five AVMs were located in the kidney parenchyma and one in the pelviureteric system. Additional associated lesions ranged from renal stones to renal cell carcinoma in two cases (one lymphangioma and one AVM). One AVM was associated with a capillary hemangioma in the vicinity, and another with a history of renal cell carcinoma in the contralateral kidney. Capillary hemangiomas and lymphangiomas were noninfiltrative and lacked cytological atypia and mitotic activity. Except for a renal pelvic AVM, all other renal AVMs radiologically mimicked malignancy. The patients had undergone partial or radical nephrectomies except for the renal pelvic AVM which was laparoscopically excised. To the best of our knowledge, none of the cases had any syndromic/systemic associations. Benign vascular lesions of the kidney are rarely seen in routine surgical pathology practice, partly because a vast majority of them are medically treated by embolization. However, lesions mimicking renal malignancy are subjected to surgery. They may exist as isolated lesions or coexist with malignant lesions either in the ipsilateral or the contralateral kidney.