Non-epithelial Renal Neoplasms of the Adult Kidney

Abstract

Non-epithelial renal neoplasms are usually incidentally discovered and generally appear as solid enhancing lesions on computerized tomography. Mesenchymal lesions include angiomyolipoma, leiomyoma, hemangioma, solitary fibrous tumor, leiomyosarcoma, synovial sarcoma, and liposarcoma, with appearances and behaviors similar to those arising outside the kidney. Angiomyolipomas are the most common of these entities and classically contain varying amounts of adipose tissue, smooth muscle, and vessels. In contrast to classic angiomyolipoma, epithelioid angiomyolipoma can be associated with a malignant outcome. Other renal-specific mesenchymal renal neoplasms include juxtaglomerular cell tumor and renomedullary interstitial cell tumor, both of which represent benign entities. The primary therapy for most mesenchymal renal neoplasms is surgical excision with concomitant partial or complete resection of adjacent uninvolved structures when locally invasive. Embolization is another option, with chemotherapy and radiation mostly reserved for palliative purposes. In addition to mesenchymal lesions, the kidney may be involved rarely by primary renal lymphoma and have secondary involvement by lymphoma and leukemia. Finally, neuroendocrine lesions may also occur and represent a spectrum of entities ranging from renal carcinoid tumor to small cell carcinoma.