The most reliable way to identify renal cyst and cystic kidney cancer is to do pathologic examination. In addition, it can also be identified by imaging examination and clinical symptoms. 1. Pathologic examination: Pathologic examination is the gold standard to distinguish renal cyst and cystic kidney cancer. Renal cysts can show benign features such as inflammatory cell infiltration or fibrous tissue proliferation, while cystic renal carcinoma can show a large number of cancer cell clusters. 2. Imaging examination: cystic renal cancer manifests as a soft tissue mass in the kidney, which is hypointense on CT and irregularly strengthened after enhancement. On the other hand, cystic renal carcinoma manifests as cystic mass of the kidney with significantly reduced density. 3. Clinical symptoms: The typical symptom of kidney cancer is renal cancer triad, which manifests as abdominal mass, lumbar pain and hematuria. Kidney cysts usually have no obvious clinical symptoms, but only a few patients have lumbar and abdominal pain, abdominal mass and so on due to the increase of cysts or the pressure inside the cysts, and in serious cases, high blood pressure or proteinuria will occur. It is recommended that patients go to the hospital to do the appropriate examination, according to the results of the examination under the guidance of the doctor active treatment.