Carcinoma of Unknown Primary

Carcinoma of unknown primary (CUP) is when you have metastatic cancer, but healthcare providers aren’t sure where the cancer began.

Metastatic cancer is cancer that spreads from where it started (primary cancer or primary tumor) to another area of your body. Healthcare providers may use the term “secondary cancer” when they talk about metastatic cancer.

Providers use information about the primary tumor to develop treatment that targets the metastatic cancer or secondary cancer. But they can also treat carcinoma of unknown primary even when they can’t find the primary tumor. Test results may give them enough information to treat CUP with specific anticancer medication.

A provider might not be able to determine the primary tumor if:

• It’s so small that imaging tests can’t detect it.
• Your immune system destroys the primary tumor.
• Surgery done for another reason removes the primary tumor.

Symptoms

Carcinoma of unknown primary may cause several common cancer symptoms. Any change in your body that doesn’t go away or gets worse is a reason to talk to a healthcare provider. Issues or symptoms that cancer can cause include:

• Cough that doesn’t clear up
• Digestive issues like a bloated belly, constipation or diarrhea
• Fatigue
• Feeling full even when you don’t eat a lot or unexplained weight loss
• Fever for no known reason
• Lump in any part of your body that doesn’t go away or becomes painful
• Night sweats
• Pain in your chest or abdomen
• Peeing more than usual (frequent urination)
• Swollen lymph nodes in your collarbone, neck, groin or under your arms

Carcinoma of unknown primary causes

Healthcare providers diagnose carcinoma of unknown primary when they can’t find the primary tumor. This can happen if the primary tumor was removed during an unrelated surgery or if tests don’t detect it.

How doctors diagnose carcinoma of unknown primary

Diagnosing CUP takes time. Healthcare providers’ first step is to try to identify the primary cancer. A provider will start that process by doing a physical examination. They’ll ask about your symptoms and current health issues. Your provider may ask about your health history and your family’s health history. They may ask about the specific medication, vitamins and supplements you take. Initial tests to diagnose CUP may include:

• Complete blood count
• Basic metabolic panel
• Fecal occult blood test
• Urinalysis

These tests may detect changes that cancer can cause. If so, your provider may refer you to an oncologist. That provider may do a biopsy to get tissue samples. A medical pathologist will examine the samples under a microscope.

Certain types of cancer change your cells’ appearance. Your pathologist will examine your cells for signs that may link the cells to a specific cancer. They may do other tests on the tissue sample like genetic testing, immunohistochemistry or to study the cells’ DNA to see where the cancer started.

Your oncologist may do other tests as well, including:

• Imaging tests like CT scans, MRI and PET scans to see how far the cancer is spreading or where it may have started
• Endoscopy to check your organs and tissues
• Tumor marker test to look for signs of substances that certain kinds of cancer release into your blood

How is carcinoma of unknown primary treated?

Your cancer care team will develop a treatment plan based on what they learn about the cancer. In some cases, pathologists can identify the primary cancer. In that case, your care team will tailor treatment to that cancer type. Your team may do more general treatment if tests don’t identify the primary cancer. Your treatment may include:

• Surgery. You may have cancer surgery to remove cancer that only affects one area of your body.
• Chemotherapy. Your care team may recommend chemotherapy if it appears you have cancer in more than one area of your body.
• Hormone therapy. Some cancers need hormones to grow. Hormone therapy works by blocking cancerous cells’ access to certain hormones.
• Immunotherapy. This treatment uses your immune system to find and kill cancer cells.
• Radiation therapy. This is treatment for cancer that appears to be in one area of your body. You may have external beam radiation therapy or internal radiation.
• Targeted therapy. You may have this treatment if tests reveal the original cancer type.

Can carcinoma of unknown primary be prevented?

You may not be able to prevent the cancer that leads to CUP. But there are ways to reduce your risk of developing cancer in the first place:

• Stop smoking if you smoke. Smoking increases the risk of many cancers.
• Cut back or stop drinking beverages that contain alcohol.
• Eat well by filling your plate with vegetables, fruits, beans, legumes and lean proteins.
• Maintain a weight that’s healthy for you.
• Wear sunscreen, hats and other protective clothing to reduce skin cancer risk.

What is the survival rate for CUP cancer?

Survival rates vary depending on factors like:

• The cancer type
• How far cancer spreads in your body
• Whether treatment is effective
• Your health

It’s important to remember that cancer survival rates are estimates. The estimates reflect the experiences of other people with cancer. Your situation may be very different. Ask your oncologist what you can expect, given your situation.

Carcinoma of unknown primary may come back after treatment. Your oncologist may recommend that you consider participating in a clinical trial.

You may benefit from mental health support. Research shows people with carcinoma of unknown primary are more likely to have depression and anxiety than others who have metastatic cancer. You may benefit from mental health support like talking to a counselor or psychologist.