A mass discovered on a kidney can raise concerns about cancer, but not all are cancerous. Many kidney masses are benign, meaning they are not cancer and typically do not spread to other parts of the body.
Kidney masses are a common finding, often discovered incidentally during imaging tests for unrelated health issues. While some masses are malignant, a significant portion are non-cancerous. A medical evaluation is always necessary to determine the nature of any kidney mass and to guide appropriate next steps.
Types of Non-Cancerous Kidney Masses
Many kidney masses are benign, posing little to no threat and often requiring no active treatment. Simple kidney cysts are the most common non-cancerous kidney mass. These fluid-filled sacs are common in individuals over 50 years old. Simple cysts are harmless and usually do not cause symptoms or require intervention.
Complex cysts might have thicker walls or internal structures, which can sometimes warrant monitoring. The Bosniak classification system categorizes kidney cysts based on imaging features, ranging from Bosniak I (simple, benign) to Bosniak IV (solid, likely cancerous). Angiomyolipomas (AMLs) are another common type of benign kidney mass. These tumors are composed of fat, blood vessels, and smooth muscle tissue. While generally non-cancerous, larger AMLs, particularly those over 4 cm, can carry a risk of bleeding and may require intervention.
Oncocytomas are benign kidney tumors that can grow large. Their appearance on imaging can sometimes resemble cancerous tumors, making differentiation challenging without further investigation. Other less common benign masses include papillary renal adenomas, which are often small and asymptomatic.
Types of Cancerous Kidney Masses
While many kidney masses are benign, some are malignant, meaning they are cancerous and have the potential to spread. Renal cell carcinoma (RCC) is the most common kidney cancer in adults, accounting for the vast majority of kidney malignancies. RCC originates in the lining of the small tubes within the kidney. It can appear as a single tumor, or in some cases, multiple tumors may be present in one or both kidneys.
Several subtypes of RCC exist, with clear cell renal cell carcinoma being the most prevalent. Other subtypes include papillary RCC and chromophobe RCC. Papillary RCC can be further divided into type 1 and type 2, with type 1 generally growing more slowly.
Other less common kidney cancers include transitional cell carcinoma and Wilms’ tumor. Transitional cell carcinoma develops in the renal pelvis. Wilms’ tumor is a type of kidney cancer primarily found in children. Early detection is important for effective treatment.
Diagnosing a Kidney Mass
When a kidney mass is identified, medical professionals employ various diagnostic tools to determine its nature. Imaging is typically the first step in characterizing a kidney mass. Ultrasound distinguishes between fluid-filled cysts and solid masses, providing initial clues about the mass’s composition. CT scans offer detailed images of the mass’s size, shape, and location. MRI provides additional detail, useful for evaluating venous involvement or avoiding radiation.
These often differentiate between benign and malignant characteristics, though some overlap exists. For instance, macroscopic fat on a CT scan can indicate a benign angiomyolipoma. In certain situations, a kidney biopsy may be recommended to obtain a tissue sample for microscopic examination. This involves inserting a needle into the mass to collect cells for analysis. While imaging suggests the mass’s nature, a biopsy provides a definitive diagnosis by confirming cell types, guiding treatment.
What Happens After a Kidney Mass Diagnosis
Management depends on whether the mass is benign or cancerous, its size, and the patient’s overall health. Many benign masses, like simple cysts, require no treatment and are monitored. Larger or symptomatic benign lesions, such as angiomyolipomas with bleeding risk, might require intervention. Active surveillance, involving regular imaging, is suitable for some benign masses.
For cancerous masses, treatment varies by tumor type, size, and stage. Surgery is a common approach for localized kidney cancer. This can involve partial nephrectomy, removing only the cancerous part while preserving healthy tissue. Alternatively, radical nephrectomy, removing the entire kidney, may be necessary for larger or complex tumors. Minimally invasive techniques like laparoscopy or robotic surgery are often used.
Other treatments include ablation techniques like cryoablation (freezing cancer cells) and radiofrequency ablation (using heat). These are considered for smaller tumors or patients unsuitable for surgery. For advanced cases, systemic therapies like targeted therapy and immunotherapy may be employed. Active surveillance is also an option for small, low-risk cancerous tumors, especially in older patients or those with other health conditions. This involves close monitoring with imaging and may avoid immediate invasive treatment.