Kidney cancer is 3% of all tumors in the adult.  In children Wilms tumor is 6% of all pediatric tumors.
Kidney cancer incidence is higher in western countries. Cigarette smoking is a recognized risk factor. Other factors include excess of phenacetin-containing drugs, and dialysis.
Family history and a rare congenital syndrome (von Hippel-Lindau) are related to an increased cancer frequency.
The incidence peak is between 50 and 70 years, with a male:female ratio of 2:1.
Renal cell carcinoma accounts for about 85% of all renal cancers. Less usual, but not uncommon, urothelial cancer may affect the urinary mucosa of the renal excretory way

In 50% of cases a bladder cancer can be associated. Often the first symptom of renal cancer is haematuria (blood in urine). Less specific symptoms include flank weight, fever, and hypertension. In advanced cancer, fatigue and lower limbs edema may occur. Sudden onset of a significant varicocele (dilatation of the vein of the testis) in adult should always be investigated, for the possible vein compression due to renal cancer. In the era of non invasive diagnostic tools, is not rare the incidental finding of a renal cancer with abdominal ultrasound or CT scan.

When a renal cancer is suspected, usually the first approach is a ultrasound of the kidney. However, the main tests for proper diagnosis and clinical staging of renal cancer are abdominal CT scan

or Magnetic Resonance; cancer site and extension can be evaluated with precision. Since renal cancer can spread to lung and brain, CT scan should be extended to chest and brain.
Bone metastases arise in the late course of disease, but if they are suspected a bone scan must be performed.
Rarely kidney cancer can appear with a cystic aspect. Because benign renal cysts are very common, sometimes the diagnosis is not easy. A cyst with thick wall, with solid tissue inside the lumen, with calcifications, should raise the suspect of a cancer, especially if they grow fast. In these cases, they deserve surgical exploration.

TNM classification of kidney cancer

Prumary Tumor (T)

TX	Primary tumor cannot be assessed (information not available).
T0	No evidence of primary tumor.
T1a	Tumor is 4 cm (about 11/2 inches) or less in diameter or and is limited to the kidney.
T1b	Tumor is larger than 4 cm but not larger than 7 cm (about 2¾ inches) in diameter and is limited to the kidney.
T2	Tumor is larger than 7 cm in diameter but is still limited to the kidney.
T3a	Tumor spread into the adrenal gland or into fatty tissue around the kidney, but not beyond Gerota's fascia.
T3b	Tumor spread into renal vein and/or the part of the vena cava, still within the abdomen.
T3c	Tumor spread into vena within the chest or invading the wall of the vena cava.
T4	Tumor spread beyond Gerota's fascia

Regional lymph nodes (N)

NX	Regional lymph nodes cannot be assessed (information not available).
N0	No spread to regional lymph nodes.
N1	Spread to 1 regional lymph node.
N2	Spread to more than 1 regional lymph node.

Distant metastasis (M)

MX	Presence of distant metastasis cannot be assessed (information not available).
M0	No spread to distant lymph nodes or other organs.
M1	Distant metastasis is present; includes spread to distant lymph nodes and/or to other organs (such as the lungs, bones, or brain).

Stage

Stage I

T1a-T1b, N0, M0: The tumor is 7 cm or less in diameter and limited to the kidney. There is no spread to lymph nodes or distant organs.

Stage II

T2, N0, M0: The tumor is larger than 7 cm in diameter but is still limited to the kidney. There is no spread to lymph nodes or distant organs

Stage III: Different combinations of T and N categories are included in this stage.

T3a-T3c, N0, M0: The main tumor has reached the adrenal gland, the fatty tissue around the kidney, the renal vein, and/or vena cava It has not spread beyond Gerota's fascia. There is no spread to lymph nodes or distant organs.

T1a-T3c, N1, M0: The main tumor has any size and may be outside the kidney, but it has not spread beyond Gerota's fascia. The cancer has spread to 1 regional lymph node but has not spread to distant lymph nodes or other organs.

Stage IV: Several combinations of T, N, and M categories are included in this stage.

T4, N0-N1, M0: The main tumor has invaded beyond Gerota's fascia. It has spread to no more than 1 regional lymph node. It has not spread to distant lymph nodes or other organs.

Any T, N2, M0: The main tumor has any size and may be outside the kidney. The cancer has spread to more than 1 regional lymph node but has not spread to distant lymph nodes or other organs.

Any T, Any N, M1: The main tumor can be any size and may be outside the kidney. It may or may not have spread to regional lymph nodes. It has spread to distant lymph nodes and/or other organs.

Radical nephrectomy (removal of the kidney with surrounding fat tissue) is the standard treatment of renal cancer. Nephrectomy can be performed either with open or laparoscopic approach.With laparoscopy, CO2 is insufflated in the abdomen. A microcamera and a few ports (trocars), 5 to 12 mm in diameter, are introduced through small holes in the abdominal wall

The operation is performed with delicate and long instruments introduced through the trocar, guided on a screen.
Since 2006 the guidelines European Association of Urology advocate laparoscopic nephrectomy for the treatment of localized kidney cancer, for decreased surgical trauma and faster recovery.
Ten-year oncological results of laparoscopy radical nephrectomy are comparable to the ones of open surgery. Even when the tumor extends to the vena cava, if the vein wall is not infiltrated and the tumor is completely removed, healing chance can be high.
Usually, if the controlateral kidney is healthy, the quality of life after nephrectomy is excellent.
However, complete removal of the kidney for cancer is not always necessary. For peripheral tumors, not larger than 4 cm (even if sometimes tumors up to 7 cm can be treated), and not involving the vascular hilum of the kidney, a partial nephrectomy is a feasible option. The tumor is resected with a thin layer (between 3 and 5 mm) of healthy tissue all around. The renal vessels are often temporary occluded, to reduce blood loss during tumor resection. The kidney tissue is then sutured. This technique is named partial nephrectomy.
In long term studies, partial nephrectomy has shown to be equivalent to radical nephrectomy at 15 years of followup. This procedure too can be performed with laparoscopic approach, but the technical complexity requires laparoscopic skilled hospitals. 
Recently, cryotherapy or radiofrequency treatment has been proposed for small peripheral tumors in very old or high risk patients. Small probes must be inserted in the tumor, trough a percutaneous or a laparoscopic approach. The tumor is thhn "freezed" at very low temperature, or heated with electromagnetic waves.
Though promising, these procedures should be considered investigative. After radical nephrectomy for non-metastatic kidney cancer, 5-years survival is 85%.
Nearly 20-30% of patients after radical nephrectomy will develop local or distant disease recurrence.
About 25% of patients with kidney cancer present distant metastasis at diagnosis. Some reports have shown that for metastatic disease, nephrectomy plus immunotherapy can be a choice for patients with good performance status and asymptomatic. However, even if survival may be prolonged, the prognosis in these patients is often poor.
In selected cases of single, amenable of surgical removal metastasis, nephrectomy plus metastasis resection is a feasible option.