The pain of 2.5*2.5 cm tumor on kidney is obvious, which may be caused by renal cancer, neuroblastoma, renal malignant tumor, renal metastasis tumor and so on. 1. Renal cancer: renal cancer is the most common primary malignant tumor of kidney, mostly seen in middle-aged and old-aged men, and patients have no obvious symptoms in the early stage. When the tumor gradually increases and pulls the renal peritoneum or invades the surrounding tissues (peritoneum or nerves, etc.), it can cause lumbago. 2. Nephroblastoma: Nephroblastoma is a malignant tumor of renal embryonic tissue origin, which is common in children, and most of them develop before 5 years old. 3. Nephroblastoma: Nephroblastoma, also known as renal vascular smooth muscle lipoma, is a common benign renal tumor. There is no obvious symptom when the tumor size is small, but when it is complicated by intra-tumor hemorrhage, it can be manifested as sudden pain. 4. Renal metastatic tumor: many malignant tumors in other parts of the body can metastasize to the kidney to form secondary tumors, if there is a history of malignant tumors in the past, renal tumors should be considered as metastatic tumors. If you find a 2.5*2.5 tumor on the kidney is painful, it is recommended that you go to the hospital as soon as possible to get a clear picture of the nature of the tumor and treat it accordingly.