Renal cell carcinoma (RCC) is the most common form of kidney cancer. Around 90 percent of all kidney cancers can be attributed to RCC.

The different types of RCC are generally distinguished by the way that cancer cells appear when viewed under a microscope. Keep reading to learn about the five different subtypes.

In the most common type of RCC, called clear cell or conventional, the cells have a clear or pale appearance. Around 70 percent of individuals with renal cell cancer have clear cell RCC. The growth of these cells can be either slow or fast.

The American Society of Clinical Oncology (ASCO) notes that clear cell RCC often responds well to treatment, such as immunotherapy and treatment that targets certain proteins or genes.

After clear cell RCC, papillary RCC is the next most common form of renal cell cancer. Under a microscope, the cells have projections that look like fingers. Approximately 10 to 15 percent of people with RCC have this type. Papillary RCC is divided into two further subtypes, known as type 1 and type 2.

Papillary RCC is generally treated using the same methods as clear cell RCC. However, targeted therapy may not work as well for people with papillary RCC.

Only about 5 percent of people with RCC have the chromophobe subtype.

Although these rare cancer cells may look similar to clear cell RCC, they tend to be bigger and have other distinguishing microscopic features.

Chromophobe RCC tends to be a less aggressive form of the disease. That’s because the tumors can grow to be quite large before spreading to different parts of the body.

Another rare form of renal cell cancer is oncocytoma. This type accounts for around 5 to 10 percent of kidney tumors.

As with chromophobe RCC, oncocytoma tumors only rarely spread beyond the kidney, making it less deadly than other forms. The tumors are also very slow growing and are more likely to be benign or noncancerous. The tumors may grow quite large, however, but can be removed through surgery.

Another rare subtype is collecting duct RCC. This type accounts for less than 1 percent of kidney tumors. It appears most often in young adults.

In this form of the condition, the cells can appear as irregular tubes under a microscope. While collecting duct RCC is uncommon, it can be aggressive. It can also be resistant to traditional treatments that are effective for other kidney tumor types.

In addition to the five main types of RCC, there are kidney tumors that don’t fit in any of the other categories. This is because such a tumor has more than one cell type visible under a microscope.

These tumors are rare, accounting for only 3 to 5 percent of RCC tumors, but they can be quite aggressive and require prompt treatment.

Each type of RCC requires its own recommended course of treatment, so it’s important for your doctor to determine which one you have quickly. If kidney cancer spreads, it’s more challenging to successfully treat.

It’s also possible that more than one tumor is present in one kidney. In some cases, you may have multiple tumors in both kidneys.

Talk to your doctor about kidney cancer, and find out what you need to know about treatment options.