Oncocytoma of the Kidney

This is a pretty cool, more rare gross finding. An oncocytoma of the kidney is actually a benign tumor (non cancerous) but does cause enough issues that it needs to be surgically removed. These tumors rarely become malignant and metastasize. Sometimes this tumor can be seen on imaging because it has a very specific appearance with a central scar. The true diagnosis of an oncocytoma can not be made until it is received in the pathology laboratory and grossly and microscopically examined. The presence of a scar alone does not mean this is an oncocytoma, scars can be seen in cancerous kidney tumors as well, but it is less likely. Scars are more common in benign tumors because they are slow growing. The center of the tumor can “die off” because of lack of blood supply. In slow growing tumors, the center tissue has time to repair itself causing a scar. Because malignant tumors are usually faster growing the center dies and does not have time to heal itself before it is surgically removed. Malignant tumors can have a central area of necrosis or dead tissue.

This is what an oncocytoma would like like on CT imaging. The red arrows are pointing to the oncocytoma tumor in the kidney.

Grossly it is smooth, homogenous and said to have a mahogany color with a central scar. I have seen a few and the color can range from a tan-orange to a red- brown mahogany color. The location of this particular oncocytoma is in the upper/mid pole and is rather large. It is very close to the hilium (which is where the ureter and renal vein and artery enter the kidney). This tumor could not be removed (partial nephrectomy) because of the location to these delicate structures so the surgeon had to do a radical nephrectomy (removal of entire kidney and a portion of the ureter).

Closer examination of the tumor shows the scar.

Most cases of renal oncocytomas are asymptomatic, discovered incidentally on CT or ultrasound imaging of the abdomen. Some of the possible symptoms are: hematuria (bloody urine), flank pain and abdominal mass.

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Disclaimer. All materials posted on my website are intended to showcase my love of pathology and art and the correlation between the two. In no way am I trying to exploit any patients or their specimens. All images and information should be used to educated people in the pathology field and enlighten others into my profession. Enjoy.