In the past few years, physicians have discovered through research that there are several different pathological classifications of renal cell carcinoma. Each classification has a specific presentation under the microscope, and almost every classification has its own specific genetic alterations.
Clear cell carcinoma
The most common type of kidney cancer is the conventional type of kidney cancer or clear cell carcinoma, which accounts for 75% to 80% of all kidney cancers. These tumors have a richer blood supply (have more inflow and outflow of blood), and overall they are more aggressive than other types of kidney cancer. More than 80% of clear cell carcinomas have mutations in the VHL gene on chromosome 3.
Papillary carcinoma
The second most common type of kidney cancer is papillary carcinoma, which accounts for about 10% to 15% of kidney cancers. The vast majority are caused by mutations on chromosomes 7 and 17. These tumors are usually not hyperemic, and are often multifocal, or have multiple small tumors surrounding the main large tumor, commonly known as “satellite tumors. The most common type of papillary carcinoma is the type 1 papillary carcinoma, which is less aggressive and has a better prognosis, and the type 2 papillary carcinoma, which is atypical, highly aggressive, and has a worse prognosis.
Smoldering renal cell carcinoma
The third type of kidney cancer is suspicious renal cell carcinoma, which accounts for 3% to 5% of kidney cancers. Its genetic mutations include multiple chromosomes, but the exact genetic localization is still being studied. These tumors are less aggressive than clear cell carcinoma and have a relatively low likelihood of extrarenal invasion or distant metastasis.
Other rare types
There are also some relatively rare types of renal cell carcinoma, including renal collecting duct carcinoma and renal medullary carcinoma, as well as some renal tumors that appear too bizarre to classify under the microscope and are often referred to as “unclassified carcinomas.
In addition, the latest 2016 edition of the WHO (World Health Organization) Classification of Kidney Tumors includes 6 new subtypes of renal cell carcinoma, all of which are very rare renal cell carcinomas, including:
- Hereditary smooth muscle tumor disease and renal cell carcinoma syndrome-associated renal cell carcinoma
- t(6;11) renal carcinoma
- succinate dehydrogenase-deficient renal carcinoma
- Tubular cystic carcinoma
- Acquired cystic nephropathy-associated renal cell carcinoma
- clear cell papillary renal cell carcinoma