Most kidney cancers (approximately 95%) originate from cells in the tubular system of the kidneys, the tissue responsible for urine production. Much less often, malignant tumors occur in the renal pelvis. At first, the tumor is limited to the kidney. Becoming larger in size, the tumor can break through the connective tissue capsule of the kidney and affect nearby tissues, lymph nodes or organs. The tumor can also grow into the pelvicalyceal system. Blood discharge of the tumor can in this case be determined in the urine. Through the bloodstream and lymphatic vessels, single cancer cells can reach distant organs. There they can multiply, so there are daughter tumors (metastases). Most often, metastases in renal cell carcinoma appear in the lungs, skeleton and lymph nodes, less often in the brain and liver.
The degree of spread of the tumor is an important criterion. The choice of treatment for kidney cancer in Germany depends on this. To accurately characterize the tumor, it is divided into different stages depending on the spread. The division occurs according to certain criteria, for which the main points are 3:
- Tumor size (T)
- Involvement of lymph nodesN)
- Presence of metastases (M)
Therefore, the term "T" is used.NM-classification. Precise determination of TNM-stage is often possible only after surgical removal of the tumor. The next item that plays a role in giving a tumor characterization is the structure of the cancerous tissue (grading). The structure of the taken tissue is studied under a microscope, and the degree of aggressiveness of the tumor is revealed. With the help of microscopic examination, it is also possible to determine what type of kidney cancer we are talking about. The result of determining the extent of the tumor and the data of the histological examination help the doctor when planning the treatment of kidney cancer in Germany.