Small benign tumor composed of renomedullary interstitial cells.
Some have suggested that these tumors may have developed as response to hypertension.
Almost all are incidental finding, found in up to 40% of adult autopsies.
Small (<5mm), well circumscribed pale gray solid nodules in the medulla (image A).
May be multiple or very rarely may form larger mass.
Relatively acellular, with small stellate cells and entrapped renal tubules in a connective tissue matrix (image B).