What would be the differential diagnosis?
a. Renal cell carcinoma b. Oncocytoma
What radiological feature is said to be helpful in suggesting an oncocytoma? Despite it not being present in this case, can this lesion still be an oncocytoma?
Central stellate scar is relatively characteristic of oncocytomas. It is however only seen in 1/3rd of cases. It may also also be sometimes seen in renal cell carcinoma. In spite of absence of central scar, the case is still indeterminate on radiological imaging.
What would be the next step for the urologist? Biopsy confirmation or directly scheduling for partial nephrectomy?
Biopsy is usually indeterminate, as renal cell carcinoma may have oncocytic elements too. Partial nephrectomy is the best option. Additionally, although thought to be less of a concern than initially believed, this eliminates the potential risk of tumour seeding during biopsy.
Other than the possibility that this represents an oncocytoma, and thus relatively benign, what other reason, in this particular case, should push the surgeon towards renal sparing surgery?
Left kidney is atrophic with thinning of parenchyma, and the patient likely has renal impairment.
In the lower pole, there is a round enhancing lesion measuring 3.1 cm in diameter without internal calcification. No apparent extension into the IVC. Only tiny para-aortic nodes evident. A few simple cysts are noted elsewhere in the right kidney. There are cysts in the left kidney as well.
The left kidney is relatively small, measuring 8.6 cm as opposed to 11.3 cm on the right side. The cortex on the left side is also relatively thinned.