Kidney tumours (or kidney tumors), also known as renal tumours, are tumours, or growths, on or in the kidney. These growths can be benign or malignant (cancerous). They may be discovered on medical imaging incidentally (i.e. an incidentaloma), or may be present in patients as an abdominal mass, hematuria, abdominal pain, or manifest first in a paraneoplastic syndrome that seems unrelated to the kidney.