Renal cell carcinoma (RCC) is the most common type of kidney cancer, accounting for approximately 90% of kidney cancer diagnoses. It develops when cells within the tiny filtering tubes of the kidneys grow uncontrollably, forming a tumor. Like many cancers, RCC has the ability to spread from its original site to other areas of the body, a process known as metastasis. Understanding how and where this spread occurs is important for comprehending the disease’s progression.
How Renal Cell Carcinoma Spreads
Renal cell carcinoma can spread through two primary pathways. One common route is hematogenous spread, where cancer cells detach from the primary tumor and enter the bloodstream. These circulating cells can then travel through the body’s vast network of blood vessels, eventually settling in distant organs and forming new tumors.
Another relevant pathway is lymphatic spread, involving the lymphatic system, a network of vessels and nodes that are part of the immune system. Cancer cells can enter these lymphatic vessels and travel to nearby or distant lymph nodes. While less frequent for RCC, the lymphatic system also facilitates dissemination.
Common Sites of RCC Metastasis
Renal cell carcinoma most frequently spreads to specific organs, with the lungs being a very common site, affecting over 50% of patients. This is primarily because blood from the kidneys circulates through the lungs, making them a common first stop for circulating cancer cells. Lung metastases can lead to symptoms such as shortness of breath or a cough.
Bones are another frequent site of metastasis, affecting approximately 20-36% of patients. Common bone sites include the spine, pelvis, and long bones. When RCC spreads to bones, it can cause pain or increase the risk of fractures. The liver also serves as a common metastatic site, observed in about 18-21% of cases. The liver’s role in filtering blood makes it susceptible to receiving cancer cells carried through the bloodstream.
While less common than lung or bone involvement, the brain can also be a site for RCC metastasis, occurring in about 8-10% of patients. Brain metastases can lead to neurological symptoms such as headaches, seizures, or dizziness. The adrenal glands, located directly above the kidneys, are also susceptible to spread due to their proximity. Other less common sites of metastasis include the pancreas, thyroid, and skin.
Understanding Metastatic RCC
The spread of renal cell carcinoma is a significant factor in determining the stage of the disease. Cancer staging, often using the TNM (tumor, node, metastasis) system, helps medical professionals understand the extent of the cancer’s progression.
Symptoms associated with metastatic RCC depend on the specific location where the cancer has spread. For example, cancer in the lungs might cause shortness of breath, while bone metastases can lead to pain or fractures. If the cancer reaches the liver, symptoms may include jaundice or swelling in the abdomen. When the brain is affected, neurological issues such as headaches or seizures can occur.
Detecting the spread of RCC typically involves various imaging tests. Computed tomography (CT) scans and magnetic resonance imaging (MRI) are commonly used to identify metastatic lesions in the abdomen, pelvis, and other areas. Bone scans may be employed if there is suspicion of spread to the bones. Ongoing monitoring is often required to assess disease activity.