Malignant tumors of the kidneys can originate from various tissues. Renal cell carcinomas (also called renal cell carcinomas or adenocarcinomas of the kidneys) are by far the most common. They make up about 95% of all kidney tumors and originate primarily from cells in the urinary tubules (tubular system). A special form (approximately 4% tumors) - oncocytoma - looks the same as renal carcinoma, but does not metastasize. Tumors of the renal pelvis are much less common.
In their microscopic structure, they are similar to malignant tumors of the bladder and ureters and therefore they are treated differently from renal cell carcinomas. In addition, there are malignant tumors that do not originate in the kidney tissue, such as lymphomas - cancers of the lymphatic tissue, sarcomas - developing in the muscles. They, like nephroblastomas, are rare in adults. Nephroblastoma, also called Wilms tumor, is a malignant tumor of the kidneys that occurs almost exclusively in children under 5 years of age.
In the following, we will focus only on renal cell carcinomas. As a rule, only one of the kidneys is affected by the tumor. Most patients do not experience problems with urination, thanks to a second healthy kidney. Rarely, about 1.5% patients later develop carcinoma in the other kidney, and even more rarely both kidneys are affected at the same time. In these cases, there is mainly a genetic predisposition to kidney cancer. As a rule, it is already known to the victims due to other typical concomitant diseases.
Kidney cancer is a relatively rare tumor disease. According to the latest estimates from the Robert Koch Institute, approximately 10,000 men and 6,500 women need treatment for kidney cancer in Germany each year. Thus, renal cell carcinoma accounts for approximately 2% of all solid malignant tumors, the trend is increasing. Young people are relatively rarely affected. Especially often kidney cancer is diagnosed between the forties and sixties of life. The average age of the diseased in men is about 65 years, in women - about 70 years. Approximately 1.5% patients develop carcinoma in both kidneys.
Currently, kidney cancer is diagnosed more often already in the early stages and can then be successfully treated. Responsible for this positive development is the frequent use of ultrasound examinations, in which the majority of kidney tumors are found by chance, as part of another examination of the abdominal cavity. At advanced stages of the disease, the prognosis of kidney cancer treatment in Germany for recovery is rather unfavorable.