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Carcinoma of unknown primary

Also called: Cancer of unknown primary, Unknown primary cancer, Occult primary

Cancer that has spread, where the starting point can't be found. Tests on the cancer often still guide treatment.

Share of cancersAbout 2 to 5 in 100
Key testTumor gene profiling

Overview

Doctors use scans, blood tests, and special tests on the biopsy (including gene profiling) to find the most likely starting place.

Treatment is based on that likely type and may include chemotherapy, targeted drugs, immunotherapy, surgery, or radiation.

Symptoms

Common signs:

  • Lump in the neck, armpit, or groin
  • Weight loss and tiredness

Less common

  • Belly swelling
  • Bone pain
  • Cough or shortness of breath

Look up a symptom: Bone pain that's constant or worse at night, or a lump on a bone or deep in a muscle · Losing weight without trying · Painless lump that's growing or won't go away · Swollen belly from fluid · Swollen glands

When to get medical care

Call 911Trouble breathing, heavy bleeding, a seizure, sudden confusion, or fainting: call 911.
Get care todayFever during cancer treatment, or new or quickly worsening symptoms.
See a doctor soonSymptoms lasting more than 2 to 3 weeks.

Causes

Changes in a cell's genes that make it grow out of control. Most happen by chance; some are linked to the risk factors below or to inherited genes.

Does it spread or run in families?

  • Cancer isn't contagious. You can't catch it from someone.

Who is more likely to get it

  • Older age
  • Smoking

Diagnosis

Tests look for the cause. Many people checked for these symptoms turn out not to have cancer.

Questions you may be asked

  • When symptoms started and whether they're getting worse
  • Family history of cancer
  • Past illnesses, treatments, and exposures

The exam

A physical exam, focused on where the symptoms are.

Tests

Tests, if needed:

  • Biopsy with special stains and gene profiling:
  • CT or PET-CT scan:
  • Blood tests:

Treatment

Treatment depends on the type, stage, and your overall health. A cancer care team makes a plan with you.

Self-care

  • Write down symptoms and when they started
  • Bring someone with you to appointments
  • Ask for copies of test results
  • Ask about clinical trials: they can offer new treatments
  • Quit smoking: it helps at every stage

Chemotherapy, targeted drugs, immunotherapy, surgery, or radiation.

Prevention

To lower risk or find it early:

  • Don't smoke
  • Keep up with cancer screenings

Which doctor treats this

  • Start with your primary care provider (family doctor or internist).
  • They may send you to an oncologist (cancer doctor), often working with surgeons and radiation doctors.

Living with it

  • Keep a simple notebook of symptoms, medicines, and questions for visits.
  • Ask for a survivorship care plan when treatment ends.
  • Gentle activity, like walking, can ease tiredness.
  • A cancer diagnosis can affect mood. Tell the care team if you or your family feel down or anxious.

Support groups and helplines

Back to school, work, or sports

  • Many people keep working during or after treatment.
  • Ask about changes that help, like flexible hours. Workers may be covered by the ADA.

Pregnancy and breastfeeding

  • If you're pregnant or planning to be, tell your cancer team. Some treatments can harm a baby.
  • Ask about saving eggs or sperm before treatment if you may want children later.

For caregivers

  • Go to visits when you can and take notes.
  • Keep a list of medicines, allergies, and doctors in one place.
  • Learn the warning signs that need fast care, like fever during treatment.
  • Take breaks and ask for help. Caregivers need care too.

Outlook

Outlook depends on the type and stage. Cancers found early are usually easier to treat, and treatments keep improving.

Support is available: ask about social workers, nutrition help, and support groups.

Getting ready for your visit

Bring a list of symptoms and medicines.

What to bring

  • A list of medicines and supplements
  • Notes on when symptoms started
  • Past test results and scans

Questions to ask

  • Can gene profiling tell us where it started?
  • Is there a clinical trial for me?
  • What stage is it, and what are the treatment options?
  • Are there clinical trials for me?

Research studies

Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.

Search ClinicalTrials.gov for studies on Carcinoma of unknown primary

Sources

Last updated 2026-11-13.