Kidney cancer, also known as renal cell carcinoma (RCC), originates in the lining of the tiny tubes within the kidneys that filter waste and produce urine. When kidney cancer cells spread from their original site to other parts of the body, this process is called metastasis.
How Kidney Cancer Spreads
Kidney cancer cells can detach from the primary tumor and travel to distant sites through specific pathways. One primary route is the bloodstream, known as hematogenous spread. Cancer cells enter blood vessels and circulate throughout the body, eventually settling and forming new tumors in other organs.
Another significant pathway for spread is the lymphatic system, referred to as lymphatic spread. Cancer cells can enter these lymphatic vessels and travel to nearby or distant lymph nodes, which can then act as a gateway to other organs.
Common Sites of Spread
Kidney cancer commonly spreads to several organs, primarily due to their rich blood supply, which facilitates the arrival of circulating cancer cells. The lungs are the most frequent site for kidney cancer metastasis. Symptoms of lung involvement can include a persistent cough, shortness of breath, wheezing, or chest pain.
Bones represent another common site of spread, often the second most frequent after the lungs. When kidney cancer metastasizes to bones, it most frequently affects the spine, pelvis, and long bones of the arms and legs. This can lead to significant bone pain, which is often the first symptom, and an increased risk of fractures due to weakened bone structure.
The liver is also a common destination for metastatic kidney cancer. Spread to the liver can cause symptoms such as appetite loss, unexplained weight loss, nausea, vomiting, or jaundice, which is a yellowing of the skin and eyes. Abdominal pain or swelling may also occur.
The brain is another site where kidney cancer can spread, particularly in advanced stages. Brain metastases may manifest as headaches, seizures, dizziness, or changes in coordination and balance. Numbness, tingling, weakness, or difficulties with speech can also be present.
Less Common Sites of Spread
While less frequent than the common sites, kidney cancer can also metastasize to other areas of the body. The adrenal glands, located on top of the kidneys, are one such site. Metastasis to the adrenal glands often causes no symptoms, but in some cases, patients may experience back or abdominal pain.
Distant lymph nodes, beyond those immediately surrounding the kidney, can also be affected. Skin metastases are rare but can occur, sometimes appearing as noticeable nodules or lesions. Soft tissues, including muscles or subcutaneous tissues, are another less common site for kidney cancer to spread.
Detecting the Spread
Detecting whether kidney cancer has spread involves various diagnostic methods. Imaging scans are crucial for identifying metastatic disease. Computed tomography (CT) scans of the chest, abdomen, and pelvis are commonly used to assess the extent of the disease and identify metastases.
Magnetic Resonance Imaging (MRI) provides detailed images of soft tissues and is particularly useful for detecting brain metastases or evaluating spread to other soft tissue areas. Positron Emission Tomography (PET) scans, often combined with CT (PET/CT), can detect metabolically active cancer cells throughout the body.
Biopsies involve taking a small tissue sample from a suspicious area for microscopic examination. This procedure can confirm the presence of cancer cells and determine if they are consistent with kidney cancer, even in a distant location. These diagnostic tests are essential for staging the cancer, which helps guide appropriate treatment decisions.