All tumor patients are most afraid of the word “wait”, and they always worry that one more day of waiting will delay their disease for one more day. In fact, doctors are just as anxious as patients, but the determination of pathology results is a very complicated and technical process, from the removal of tumor specimens to fixing, making paraffin specimens, sectioning, reading and reviewing, each step is quite important. Just like cooking a dish, 5 minutes less may make a big difference in taste. So it’s not as simple as saying hello and rushing the pathology. More importantly, the follow-up treatment plan of doctors depends on the pathology results. So what is the complexity of pathological results of kidney tumors? Here we introduce you to the types of renal cell carcinoma, an important piece of tumor information that can only be known through pathology. Over the past few years, doctors 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 specific genetic alterations. (1) The most common type of kidney cancer is the conventional type of kidney cancer or called clear cell carcinoma, which accounts for 75 to 80 percent of all kidney cancers. These tumors have a richer blood supply (have more inflow and outflow of blood), and overall they have a worse prognosis than other types of kidney cancer (type 2 papillary renal cell carcinoma or smallpox renal cell carcinoma). More than 80% of clear cell carcinomas have mutations in the VHL gene on chromosome 3. The majority of patients who respond to immunotherapy have clear cell carcinoma, so we used to use immunotherapy to manage clear cell carcinoma. In recent years, the control rate of renal cell carcinoma has improved significantly due to the advent of targeted therapies, and most of the clinical data for targeted therapies have come from clear cell carcinoma. Therefore, the treatment for clear cell carcinoma is more mature, with better prognostic data and more internationally recognized treatment options. (2) The second most common type of kidney cancer is papillary carcinoma or chromophobe carcinoma, which accounts for about 10% to 15% of kidney cancers. The majority of these tumors are caused by genetic 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 referred to as “satellite tumors. Based on the microscopic presentation, papillary carcinoma is divided into type 1 and type 2. Type 1 papillary carcinoma is less aggressive and has a better prognosis, while type 2 papillary carcinoma has an atypical presentation, is highly aggressive and has a worse prognosis. To put it more graphically, type 1 papillary carcinoma has a better prognosis compared to renal clear cell carcinoma, while type 2 has a worse prognosis compared to renal clear cell carcinoma. The good news is that the mainstream targeted therapies have some efficacy in papillary renal cell carcinoma, but unfortunately the tumor remission rate is not as good as it should be. (3) 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 gene localization is still under study. This type of tumor is less aggressive than clear cell carcinoma and has a relatively low likelihood of extra-renal invasion or distant metastasis, so the overall prognosis is good. Of course, if the pathology report mentions a high-grade or combined sarcomatous component, then the prognosis and treatment situation will need to make a 180-degree turn. Current clinical results suggest that some specific types of targeted agents such as the mTOR inhibitor tesirolimus can be used in the treatment of advanced smack cell carcinoma. (4) Collecting ductal carcinoma, a type of renal cell carcinoma that accounts for only 1% of kidney cancers, is relatively challenging to treat. Most ductal carcinomas are high-grade, advanced and naturally resistant to conventional kidney cancer treatment at the time of onset. In this pathological type of kidney cancer, we may need to use cisplatin or gemcitabine-based chemotherapy. (5) Sarcomatoid differentiation of renal carcinoma is found in about 1-5% of renal carcinomas, commonly in clear cell carcinoma or suspicious cell carcinoma, and this differentiation is a key piece of information to look for while we wait for the pathology report. Kidney cancer with this condition, regardless of the pathological type, has aggressive growth characteristics, rapid growth, easy metastasis and poor prognosis. In addition, there are some relatively rare renal cell carcinomas, including renal medullary-like carcinoma, MiT family ectopic-associated renal carcinoma, mucinous tubular and spindle cell carcinoma, tubular cystic renal cell carcinoma, acquired cystic disease-associated renal carcinoma, clear papillary renal cell carcinoma, HLRCC syndrome-associated renal carcinoma, and renal cell carcinoma that cannot be classified. In short, in the modern field of oncology treatment, physicians and even patients themselves are no longer satisfied with merely distinguishing the benign and malignant nature of the disease. Only a good pathology can help us maximize the information related to tumor, which is mostly related to treatment and prognosis. So, pathology, still have to wait patiently.