Kidney Cancer

Comprehensive information on the causes, symptoms, treatments, and prognosis of malignant neoplastic proliferation in renal tissue.

Symptoms and Causes

Kidney cancer, or renal carcinoma, is a disease characterized by the overgrowth of cells that form renal tissue, which accumulate to form malignant tumors.

With the increasingly widespread use of imaging tests, many cases are detected incidentally in early stages.

Based on the characteristics and origin of the neoplasms, kidney cancer can be classified into several types:

Adenocarcinoma or renal cell carcinoma (RCC): the most common type, accounting for approximately 80% of diagnoses. It usually presents as a solitary tumor within the kidney.

Clear cell carcinoma: the most frequent subtype. Cells have a clear cytoplasm due to lipid accumulation and a well-defined cell membrane.
Granular (non-clear) cell carcinoma: subdivided into several subtypes:

Papillary cell carcinoma: small in size, with papillary structures in one area or across the entire tumor surface. When stained for microscopic examination, they absorb the dye and appear pink.
Chromophobe cell carcinoma: although clear like adenocarcinomas, these cells are larger, polygonal, transparent with a pale halo, and contain numerous vesicles.
Unclassified carcinoma: exhibits features distinct from the aforementioned types, typically irregular in appearance and markedly different from healthy cells.
Rare carcinomas: in very uncommon cases, other tumor types may occur:
Transitional cell or urothelial carcinoma: originates in the renal pelvis rather than the kidney parenchyma. These tumors resemble bladder cancer, with enlarged nuclei and irregular cell morphology.
Nephroblastoma or Wilms tumor: predominantly affects children. The tumor exhibits heterogeneous morphology, comprising blastemal cells (small, round, overlapping nuclei), stromal cells (elongated and slender), and epithelial cells (tubular structures).
Renal sarcoma: arises from renal blood vessels or connective tissue, composed of clear cells with variable growth and high metastatic potential. Extremely rare.

Collecting duct carcinoma
Multilocular cystic carcinoma
Medullary carcinoma
Mucinous tubular and spindle cell carcinoma
Neuroblastoma-associated carcinoma

Kidney cancer is the eighth most common tumor in Spain. Prognosis varies significantly depending on tumor type and stage at diagnosis. Most tumors are localized and can be completely removed surgically, with a five-year survival rate of approximately 93%. However, 20–30% of patients are diagnosed after metastasis has occurred, making recovery more challenging.

Symptoms

Kidney cancer often remains asymptomatic, even in advanced stages, and is frequently detected during routine examinations. When symptoms occur, the most common include:

Flank or lower back pain
Hematuria (blood in the urine)
Loss of appetite
Palpable abdominal mass
Fatigue
Unexplained weight loss

Causes

Although the exact cause is unknown, kidney cancer arises from DNA alterations in renal cells. These changes lead to uncontrolled proliferation and prolonged cell survival compared to healthy cells. The resulting excess cells cluster to form rapidly growing malignant tumors that may invade adjacent tissues.

Risk Factors

Factors that increase the risk of developing kidney cancer include:

Age: typically occurs in individuals aged 50–70 years; Wilms tumor is more frequent in children under 5 years.
Sex: more common in men.
Smoking
Obesity
Hypertension
Advanced kidney disease, particularly in patients requiring dialysis.
Hereditary genetic syndromes, such as:

von Hippel-Lindau disease: increases the likelihood of tumors in the brain, spinal cord, pancreas, adrenal glands, and kidneys.
Birt-Hogg-Dubé syndrome: genetic mutations lead to benign skin neoplasms, pulmonary cysts, and renal tumors (benign or malignant).
Tuberous sclerosis: forms non-cancerous masses in the skin, brain, heart, lungs, or kidneys.
Cowden syndrome: typically forms cysts in the gastrointestinal tract and increases the risk of various cancers, including endometrial, breast, thyroid, colon, and kidney cancer.

Family history of kidney cancer
Genetic predisposition

Complications

Kidney cancer may lead to serious complications, including:

Hypercalcemia: elevated blood calcium levels
Erythrocytosis: abnormally high red blood cell count
Renal vein thrombosis: blood clot formation obstructing or impeding blood flow
Metastasis: spread of renal cancer to other organs, particularly the lungs, brain, bones, liver, or adrenal glands

Prevention

Although kidney cancer cannot be completely prevented, the risk can be significantly reduced by following these recommendations:

Avoid smoking
Limit alcohol consumption
Maintain a balanced diet rich in fruits and vegetables
Engage in regular physical activity
Maintain a healthy body weight

Which Specialist Treats Kidney Cancer?

Initial suspicion often arises in urology, but kidney cancer is primarily managed by medical oncology and radiation oncology specialists.

Diagnosis

The diagnostic protocol for kidney cancer includes various tests:

Blood tests: elevated red blood cells, calcium, or liver enzymes may indicate malignancy.
Urinalysis: the presence of blood or bacteria may indicate kidney disease. Cancerous cells may also be detected in urine samples.
Computed tomography (CT): X-rays, often with contrast, provide cross-sectional images from multiple angles, which can be reconstructed into a three-dimensional representation of the kidney. This imaging assesses organ characteristics, identifies abnormal masses, their location, and size.
Magnetic resonance imaging (MRI): uses radio waves and a high-strength magnetic field to produce images. MRI provides less detailed images than CT but is suitable for patients unable to undergo X-rays or with contrast allergies.
Biopsy: definitive diagnosis of kidney cancer involves obtaining a renal tissue sample for microscopic examination of malignant cells.

Cancer staging is determined using radiological imaging. Each stage presents distinct characteristics:

Stage I: tumor <7 cm, confined to the kidney
Stage II: tumor >7 cm, not extending to surrounding tissues
Stage III: tumor invades a vein (commonly renal or inferior vena cava) or surrounding tissue, without reaching the adrenal gland
Stage IV: tumor extends beyond Gerota’s fascia (fibrous tissue surrounding kidneys and adrenal glands), which may be invaded. Nearby lymph nodes may be affected, but distant metastasis is absent

Treatment

Kidney cancer treatment requires a multidisciplinary and individualized approach. The most effective interventions include:

Surgery: removal of the tumor and, in most cases, surrounding healthy tissue to ensure complete excision of cancer cells. Procedures may be open or laparoscopic, depending on patient-specific factors. Depending on tumor size and stage:

Partial nephrectomy: excision of the tumor-bearing portion of the kidney; suitable for small, localized tumors at one pole, aiming to preserve renal function
Radical nephrectomy: removal of the entire kidney, surrounding lymph nodes, and perirenal fat; allows normal life with one functioning kidney and ensures complete cancer cell removal

Ablation: for patients unsuitable for surgery with small tumors, ablation destroys tissue via cryotherapy (cold) or radiofrequency (heat) using a probe inserted directly into the tumor
Radiotherapy: selected for patients who cannot undergo surgery or have a single kidney; external radiation is applied to reduce tumor size and slow cell proliferation
Immunotherapy: drugs enhance immune response to target cancerous cell proliferation
Targeted therapy: medications address specific DNA alterations driving cancer. Common agents inhibit tumor angiogenesis or cancer cell proliferation
Chemotherapy: systemic chemical therapy shows limited efficacy in kidney cancer and is reserved as a last-line treatment when other options fail