The most dangerous types of kidney tumors are unclassified renal cell carcinoma, collecting duct carcinoma, medullary renal cell carcinoma and sarcomatoid renal cell carcinoma, explains the Kidney Cancer Association. Transitional cell carcinoma of the kidney is also very aggressive and has a poor prognosis.
Collecting duct carcinoma is a rare and very aggressive tumor that most often occurs in younger adults, explains the Memorial Sloan Kettering Cancer Center. It does not respond to traditional treatments, such as bioimmunotherapy, notes the Kidney Cancer Association.
Unclassified renal cell carcinoma does not fit into the common kidney cancer subtypes, explains the Kidney Cancer Association. Unclassified types are often very aggressive and unresponsive to traditional treatments. Medullary renal cell carcinoma is rare and aggressive, and it is associated with the sickle cell trait. Sarcomatoid renal cell carcinoma occurs with any of the kidney cancer subtypes. It metastasizes widely, and the prognosis is very poor.
Transitional cell carcinoma of the kidney develops from cells that line the urinary tract, explains the Kidney Cancer Association. Surgical removal of both kidneys and the ureter is necessary if the tumor has not spread. Recurrence and metastasis are common, and prognosis is very poor.