Abstract

We present an ultrastructure of an incidentally found renomedullary interstitial tumor also called as medullary fibroma in a 77 year-old female who had a metastatic adenocarcinoma of colon to the ureter. This tumor was a small and grayish white nodule in renal medulla, measuring 0.4 x 0.4 cm. Microscopically the tumor composed of spindle cells, with some vacuolation and intercellular collagen fibers. The electron microscopic observation of the spindle cells reveal that nuclei are spindle to oval shape and cytoplasm contain abundant rough endoplasmic reticulum, polyribosome without microfilaments and cisterna like structures supporting that the renomedullary interstitial cell tumor is renal interstitial cell origin than fibroblasts.

• Keywords: Renomedullary interstitial cell tumor;Medullary fibroma;