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People often confuse renal tumors with renal cancer. Not all renal tumors are malignant in nature. Some of them can be benign as well. Mentioned below are the renal tumors, both benign as well as malignant.
Benign Renal Tumors
As the term suggests, these tumors are noncancerous and do not metastasize. The benign renal tumors can be of the following types
Renal Adenoma: One of the most common types of benign renal tumors, renal adenoma are asymptomatic, low-grade, solid tumors which are quite small in size. It is yet not known as to what triggers the occurrence of renal adenoma. The renal adenoma seldom interferes with the normal kidney function. There may, however, be a problem if this tumor grows in size, where they mimic the RCC (Renal cell carcinoma) in their symptoms.
Angiomyolipoma: This type of benign renal tumor is rare and often triggered by a genetic mutation (inherited). Also called Renal Hamartoma, the tumor is often found to be a complication associated with Tuberous Sclerosis (a genetic condition that results in tumor formation in different body parts including the kidney). Angiomyolipoma, not triggered by Tuberous Sclerosis is often found to affect women who are middle-aged.
Renal Oncocytoma: The trigger for Renal Oncocytoma is not known. Unlike the renal adenomas, renal oncocytoma can grow quite large in size and are usually asymptomatic, with males being more susceptible to the condition. Another striking feature about renal oncocytoma is that it can occur in the other body parts as well.
Fibroma: As the name suggests, fibroma is benign tumors originating from the fibrous tissues on the kidneys or adjacent to it. These rare tumors are small in size, with the exact cause being unknown. Fibroma is asymptomatic, affecting women more than men.
Lipoma: Mainly affecting middle-aged women, lipomas are found to originate from the fat cells located within the kidney (renal capsule) or adjacent tissues. Lipomas can be painful and cause hematuria when they increase in size.
Malignant Renal Tumors
As the name suggests, there are cancerous tumors that can metastasize to other body parts. The malignant renal tumors can be of the following types
Renal cell carcinoma (RCC): Known to develop in the kidney tubules, the cancerous outgrowths can cause renal obstruction. One of the most common types of renal cancer, RCC can affect one or both of the kidneys.
Depending on the microscopic observation, RCC may further be divided into
Clear Cell RCC: Accounting for nearly 80% of the total RCC, under a microscope, the clear cell RCC appears clear and pale.
Papillary RCC: Accounting for 10-15 percent of RCC, the Papillary RCC is characterized by the formation of finger-like projections within the tumor.
Chromophobe RCC: The Chromophobe RCC are large with microscopically appearing clear and pale.
Collecting duct RCC: Being quite aggressive, cancer cells in collecting duct RCC results in the formation of irregular tubes inside the renal tumor
Transitional cell carcinoma: Also referred to as Urothelial Cancer or Renal Pelvis Carcinoma, the transitional cell carcinoma forms at the merger point of the kidney and the ureter.
Renal sarcoma: It is a rare type of renal cancer originating in the connective tissue of the kidney.