Collecting duct carcinoma (CDC) is a rare and aggressive form of kidney cancer. It develops in the Bellini duct, or the collecting duct, of the kidneys. It may cause no symptoms until it is in an advanced stage.

A person’s kidneys are part of the excretory system. The excretory system filters and removes from the body.

The kidneys each contain filtration units called nephrons. Nephrons filter a person’s blood for waste. This waste travels through the collecting duct of the nephron, where excess water is absorbed back into the bloodstream. The remaining waste travels on to the bladder, where it is eventually excreted.

Collecting duct carcinoma (CDC) affects the collecting duct of the kidneys.

Read on to learn more about CDC, including its causes, symptoms, and treatments.

Healthcare professional reviewing scansShare on Pinterest
123ducu/Getty Images

CDC is a rare form of cancer that affects the collecting ducts of the kidneys. Cancer occurs when a person’s cells begin to multiply abnormally. This can cause tumors to develop.

Information from the Kidney Cancer Research Alliance (KCCure) notes that CDC accounts for less than 3% of renal cell carcinomas (RCCs). RCC is the most common form of kidney cancer.

CDC is aggressive, which means it can develop, grow, and spread quickly. A person may not know they have CDC until it is in its advanced stages.

A case report from 2023 notes CDC generally spreads to nearby lymph nodes. Lymph nodes are small organs that contain immune system cells.

CDC may spread to areas far from the kidney, including the:

  • bones
  • liver
  • ureters, the thin tubes connecting the kidneys to the bladder
  • lungs
  • pleura, a membrane that surrounds the outside of a person’s lungs
  • pancreas
  • adrenal glands, which sit above a person’s kidneys

The Genetic and Rare Diseases Information Center (GARD) states that fewer than 1,000 people in the United States have CDC.

A person with CDC may not experience symptoms until the condition has become advanced. When they do experience symptoms, they may include:

  • pain in the side of the back
  • unexplained weight loss
  • blood in urine
  • fatigue
  • abdominal pain

GARD notes the exact cause of CDC is currently unknown. It generally occurs in people who do not have a family history of the condition.

GARD also notes that people of any age can develop CDC. However, symptoms tend to develop in younger adults.

A study from 2023 found CDC more commonly affects people assigned male at birth.

A doctor may find it difficult to diagnose a person with CDC. It has similar symptoms to other forms of RCC, which may result in a misdiagnosis. Additionally, CDC is rare, which also makes it difficult to differentiate from other forms of RCC.

An analysis from 2022 notes that a doctor may use an imaging scan to diagnose a person with CDC. A CT scan is most commonly used to check a person for signs of CDC. A CT scan uses a computer and X-rays to take a detailed picture of a person’s body.

A CDC tumor may appear on a CT scan as a lone, poorly defined, solid mass. They are generally located in the center of the kidney. A study from 2021 states that small CDC tumors may involve the renal sinus, a part of the kidney that stores fat to help cushion important areas.

Large CDC tumors may hide these distinguishing features, making CDC very difficult to diagnose.

Researchers note a CDC tumor should have the following features for a doctor to diagnose it as CDC:

  • should involve the inner part of the kidney
  • should contain mostly tube-like structures
  • present with desmoplastic stromal reaction, when a person’s body forms fibrous tissue around the tumor
  • contains moderately or severely abnormal cells
  • the tumor grows into the surrounding tissue
  • contains no signs of other forms of RCC

A doctor may take a sample of a tumor to test it for certain biomarkers. These markers may help determine the origin of the tumor.

An analysis from 2022 notes that there is no standard treatment for CDC. Doctors generally treat localized CDC by removing the kidney. A healthcare professional may not recommend surgery if CDC has already spread.

However, CDC is likely to return and spread even after surgery.

Researchers note chemotherapy may have some effect on CDC tumors. Additionally, a form of an immunotherapy drug, called immune checkpoint inhibitors (ICIs), may be effective against CDC. ICIs work by helping the immune system kill cancer cells.

However, the effectiveness of ICIs in the treatment of CDC requires further study.

A study from 2022 looked into the effectiveness of cabozantinib, a targeted therapy drug, in treating people with metastasized CDC. Metastasized cancers have spread from their place of origin to other parts of the body.

Researchers found promising results, but they note determining how effective cabozantinib is as a treatment for CDC requires further research.

The outlook for a person who has CDC is generally poor. CDC is an aggressive cancer that can spread to distant parts of the body. Metastatic CDC can reduce a person’s overall chances of survival.

Research from 2022 found that among the 58 people they followed up with, the median survival time for a person who has CDC without distant metastasis was 34 months. If a person had distant metastasis, the median survival rate was 11 months.

Healthcare professionals base survival rates on how long people with the same condition lived after their diagnosis. Many factors can affect individual survival rates, such as a person’s age, overall health, and reaction to treatment. A person should speak with a healthcare professional about their individualized outlook.

Collecting duct carcinoma is a rare form of aggressive kidney cancer. It has no clear cause or significant risk factors. A person may have no symptoms of CDC until it becomes advanced.

CDC can be difficult to differentiate from other forms of renal cell carcinoma. A doctor may use specific tests and diagnostic criteria to diagnose a person with CDC.

A healthcare professional will generally recommend removing the affected kidney. However, it has a high chance of reoccurring and spreading. Researchers are currently testing certain other treatment options, such as immune checkpoint inhibitors and targeted drug therapy, for their effectiveness against CDC.

The outlook for a person who has CDC is generally poor. An early diagnosis may help improve a person’s outlook, though. A person should discuss their individual survival rate with a healthcare professional.