Clear Cell Papillary Renal Cell Carcinoma
Clear cell papillary renal cell carcinoma is a distinct type of kidney cancer that was recognized as separate from other kidney cancers in 2006, and is now considered to have a less aggressive nature than many other forms of the disease.
Table of contents
- What Is Clear Cell Papillary Renal Cell Carcinoma
- Naming and Classification
- How Common Is This Cancer
- Symptoms
- How Is It Diagnosed
- Treatment Approaches
- Outlook and Prognosis
What Is Clear Cell Papillary Renal Cell Carcinoma
Clear cell papillary renal cell carcinoma is a specific subtype of kidney cancer that occurs when cancer cells form in the small tubes inside the kidneys. These tubes, called tubules, help filter waste products from the blood[1].
This type of kidney cancer has features that overlap with both clear cell and papillary types of renal cell carcinoma (the most common form of kidney cancer in adults), but it has distinct clinical characteristics that set it apart[1]. When doctors look at the cancer cells under a microscope, they can see various tubular and papillary structures, and the cells have an empty or clear appearance in their center[3].
Researchers first recognized clear cell papillary renal cell carcinoma as different from other subtypes of kidney cancer in 2006[1][2]. The cancer was initially discovered in patients with end stage renal disease (severe kidney failure), but it has since been found in people with normal kidney function as well[3].
Naming and Classification
CCPRCC, clear cell tubulopapillary renal cell carcinoma, CCPRCT
The name for this type of cancer has changed over time as doctors have learned more about it. Earlier terms that medical professionals used include clear cell papillary renal cell carcinoma (CCPRCC) and clear cell tubulopapillary renal cell carcinoma[1].
According to the World Health Organization’s 2022 classification of kidney tumors, health experts now typically refer to this cancer as a clear cell papillary renal cell tumor (CCPRCT). This name change reflects the understanding that this cancer has a more benign or less aggressive nature compared to other kidney cancers. The new name also helps doctors better distinguish it from more dangerous types of kidney tumors[1].
How Common Is This Cancer
Clear cell papillary renal cell carcinoma is relatively rare. It accounts for approximately 1 to 4 percent of all kidney cancers[3]. In one study that followed patients who had kidney surgery between 2016 and 2022, CCPRCT was found in 36 out of 2,057 patients, representing about 1.8 percent of cases[3].
Because this cancer is uncommon and was only recently recognized as a separate type, there is still limited information available about its clinical characteristics and long-term outcomes compared to more common forms of kidney cancer[3].
Symptoms
Most people with clear cell papillary renal cell carcinoma do not experience any noticeable symptoms, especially in the early stages. The cancer is often discovered by accident when doctors perform imaging tests for other medical reasons[3].
When the tumors are found, they tend to be quite small. In one study, the average tumor size was just 1.2 centimeters[3]. The tumors usually have well-defined borders and are mainly surrounded by a membrane or film[3].
How Is It Diagnosed
Doctors use several methods to diagnose clear cell papillary renal cell carcinoma and understand its characteristics.
Imaging tests are commonly the first step in finding kidney tumors. These may include CT scans (a type of detailed X-ray) or MRI scans (which use magnets and radio waves to create pictures of the inside of the body). However, imaging alone cannot always determine whether a kidney mass is cancerous or what specific type of cancer it might be.
A biopsy may be performed, where a doctor removes a small sample of tissue from the tumor using a needle. A specialist called a pathologist then examines the cells under a microscope to identify the specific type of cancer[3].
The microscopic examination is particularly important for diagnosing CCPRCT. Under the microscope, the cells show various tubular and papillary patterns, with a clear or empty appearance in the cytoplasm (the gel-like substance inside cells). The cancer typically has a low Fuhrman nuclear grade, which is a system doctors use to describe how abnormal the cancer cells look. The cell nuclei (control centers) are arranged in rows away from the basement membrane (the outer boundary of cells)[3].
While CCPRCT can often be distinguished from regular clear cell renal cell carcinoma on standard microscope slides, additional tests using immunohistochemistry can be helpful. Most CCPRCT tumors express a marker called cytokeratin 7 (CK7), which helps confirm the diagnosis[3].
Treatment Approaches
Surgery is the main treatment approach for clear cell papillary renal cell carcinoma. Because the tumors are typically small and have good borders, they are often suitable for less extensive surgical procedures.
In one study of 36 patients with CCPRCT, 29 patients underwent partial nephrectomy, which means surgeons removed only the tumor and a small amount of surrounding kidney tissue, leaving most of the kidney intact. Seven patients who had end-stage kidney disease underwent radical nephrectomy, where the entire kidney was removed[3].
For patients who had partial nephrectomy, the surgery took an average of 97.5 minutes, with an estimated blood loss of 100 cubic centimeters. Patients typically spent about 4 days in the hospital after surgery. Only 2 cases experienced complications classified as Clavien-Dindo level III or higher, which indicates more serious complications requiring intervention[3].
Outlook and Prognosis
- Kidneys
- Kidney tubules
The prognosis for clear cell papillary renal cell carcinoma appears to be very good. This is one of the main reasons why health experts changed its classification to include the word “tumor” rather than “carcinoma” in some contexts — to reflect its less aggressive nature[1].
No cases of spread to other parts of the body (metastasis) have been reported so far with this type of kidney cancer[3]. In the study that followed patients for an average of 26.8 months after surgery, there were no cases of cancer coming back (recurrence) and no deaths specifically caused by the cancer[3].
The tumors are generally discovered at an early stage when they are still small, and there have been no reports of advanced-stage disease at the time of diagnosis[3]. This favorable behavior makes clear cell papillary renal cell carcinoma different from more aggressive types of kidney cancer.
However, because this cancer type was only recently recognized and is relatively rare, researchers note that larger studies involving multiple medical centers are needed to better understand its long-term behavior and outcomes[3].
