renal medullary fibroma renal medullary fibroma renal medullary fibroma is a benign kidney tumour. it is commonly an incidental finding. renal medullary fibromaother namesrenomedullary interstitial cell tumou, medullary fibroma'micrograph of a renal medullary fibroma (bottom of image). renal tubules are seen at the top of the image. h&e stain. signs and symptoms renal medullary fibromas are typically asymptomatic. diagnosis renal medullary fibromas are diagnosed by pathologists based on the examination of tissue. they consist of bland spindle-shaped or stellate-shaped cells in a loose stroma. renal tubules may be entrapped. low mag. high mag. treatment generally, no treatment is required.