MRCP2-3601

A 65-year-old man presents to the clinic with complaints of left flank pain and gross haematuria. The pain is dull and not radiating, and he has not experienced any fever or chills. The patient has not sought medical attention in 15 years.
Upon examination, his vital signs and physical exam are normal. Blood tests and a biochemical profile are also normal. A CT scan of the abdomen and pelvis reveals a 6 cm mass in the lower pole of the left kidney. A chest X-ray and abdominal ultrasound are unremarkable, as is a CT scan of the thorax.
What is the most appropriate course of action for this patient?