A 36-year-old man, with no personal history of interest, who in an ultrasound scan performed due to colicky pain over the right renal fossa, was reported as an intrarenal mass measuring 8-10 cm with echogenic material inside, located in the lower pole of the right kidney, suggesting a complicated renal cyst. Subsequent CT scan showed a solid mass in the lower pole of the right kidney with a maximum diameter of 10 cm, which caused compression of the excretory tract, with no evidence of tumour thrombus in the renal vein or in the cava, suggestive of hypernephroma. Bone scintigraphy with Tc99m-MDP was performed and no pathological bone accumulations were observed. 
Based on the data obtained, a radical right nephrectomy was performed, revealing an intraoperative finding of a mass attached to the lower pole of the right kidney (the tumour and the kidney, although close together, were clearly independent on dissection).
The anatomo-pathological report of the specimen was a solitary fibrous tumour. The tumour was well demarcated but not encapsulated, without infiltrating the kidney or the renal vessels which were displaced by the large tumour mass. The immunohistochemical study showed positivity for CD34, CD99 and Vimentin, while it was negative for Desmin, Protein S-100, and CAM5.2.

The patient underwent surgery in November 2001. Since then, he has been undergoing outpatient controls in our clinic with biannual ultrasound scans and annual CT scans, with no recurrence.