I am a specialist in urologic oncology with extensive experience in the treatment and management of patients with kidney cancer and other tumors of the kidney. I have an established publication record on the details and nuances of kidney tumor surgery and optimal renal mass treatment. I am an associate professor of surgical oncology at a large cancer center in the Mid-Atlantic. I am also the director of our institution’s urologic oncology fellowship. This is a rare type of tumor and is not expected in the routine differential for a renal mass/Bosniak scale 3 abnormality. The most common anticipated result would be renal cell carcinoma or a benign renal oncocytoma. It is not possible to comment on the likelihood of this tumor causing pain or symptoms without additional details about the renal mass, such as the size and location within the affected kidney. In general, most kidney abnormalities that are small in size are typically asymptomatic. Flank pain would not be expected to be associated with a tumor unless it was very large and causing significant changes to the normal kidney. There would be no predictive imaging findings to distinguish this type of tumor from renal cancer. If there is a question as to whether a renal mass is a renal cell carcinoma, a biopsy can be applied prior to nephrectomy. It is not, however, a standard of care step that is mandatory prior to surgical treatment. What may be a separate question is whether or not the nephrectomy was the indicated procedure, or if an alternative surgery could have been offered.