Case 009 -  A 48 year old male with right renal mass

Contributed by Andre Thompson, M.D.  Supervised by Alina Jukkola, MD

Clinical History
 
The patient is a 48-year-old white male who was referred to GU Clinic for right renal mass that was an incidental finding on ultrasound.   CT showed a 4.0 cm enhancing mass in the lower pole of the right kidney.

Gross Findings

Received is a right radical nehprectomy  specimen measuring 17.5 X 11.0 X 7.5 cm and weighing 470 grams.  A well-circumscribed, 3.5 X 3.5 X 2.8 cm, tan-brown tumor is present at  the inferior pole.

Microscopic Findings

Click on the thumbnails to enlarge images.

   Image (1) Gross pathology
 

 Image (2) H&E, 2X

 

 Image (3) H&E, 4X

 

 Image (4) H&E, 20X
  Image (5) H&E, 40X
  Image (6)
Colloidal Iron, 60X

Diagnosis

Renal Oncocytoma
 
The tumor exhibits an organoid pattern with well-defined nests of tumor cells, and areas of myxoid stroma. The central, fibrous scar (image # 2) is characteristic for renal oncocytoma.   Areas of confluent nests give the appearance of a solid tumor; the nests in these areas are outlined by thin fibrous septa.  The tumor cells exhibit finely granular eosinophilic cytoplasm; round nuclei with smooth, regular contour and evenly distributed chromatin, and variable nucleoli.  The tumor cells were negative for vimentin and CK 7.  Colloidal iron stain shows periluminal positivity (unlike the diffuse positivity seen in chromophobe renal cell carcinoma).