In this section: Unknown Primary Cancer

CANCER of an unknown primary

What do we mean by 'Cancer of an Unknown Primary'? Cancer of Unknown Primary in the head and neck region occurs when the origin of the cancer is unknown, but is found to have spread to the lymph nodes in the neck. If it's not the cancer type you're looking for, please explore the information about other types of Head and Neck Cancers.

All the information in this section is available in a PDF.
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1. Symptoms and signs of Cancer of an Unknown Primary

Patients with Cancer of Unknown Primary usually notice a lump in their neck, which is usually painless. Most patients don’t have any other symptoms.

Swollen lymph nodes may be due to an infection, such as a cold or flu, but the swelling should subside after two weeks. Children and young adults may sometimes have persistently enlarged lymph nodes due to viruses such as glandular fever.

However, adults that notice a swollen lymph node that does not go away within four weeks should consult their doctor. Adults presenting with enlarged lymph nodes for a month or longer may be recommended a needle biopsy to check for cancer. 

Watch a 3D video explainer about Cancer of an Unknown Primary:


2. What are the tests for Cancer of an Unknown Primary?

For diagnosis of Cancer of Unknown Primary, your doctor will need to do the following things:

  • talk with you about your medical history. This includes discussing symptoms that might point to the source of the cancer, risk factors (e.g. smoking or drinking), and any previous history of cancer

  • perform a physical examination by examining your nose, mouth, throat, thyroid gland and skin for any suspicious areas

  • arrange a referral to a head and neck or ear, nose and throat (ENT) specialist who may order diagnostic tests such as exams or scans for further assessment.

Common tests used include:


In some patients, the primary cancer may grow slowly and be too small to be seen on examination and scans; the primary site may appear later during follow-up.

Sometimes, a biopsy of the primary site is needed to make sure there is no cancer within them, but examining these areas is often difficult when the patient is awake.

The doctor may suggest examining the areas under general anaesthesia (with you asleep) if the primary site of cancer hasn’t been identified. Whilst under anaesthesia, the doctor can perform a thorough examination of the mouth, throat, voice box and the back of the nose (nasopharynx).

Based on the examination, the doctor may recommend:​

  • Needle biopsy (Fine Needle Aspiration or FNA biopsy): This is when a thin needle is inserted into the suspicious lymph node to remove a sample. Typically this is performed using ultrasound guidance with local anaesthetic to reduce your discomfort. The tissue is then examined under a microscope to look for cancer cells by a pathologist. This is the only sure way to know if you have cancer.

  • If a diagnosis cannot be made based on the FNA, it is either repeated or a core biopsy (a similar procedure with a larger needle) may be performed. If the diagnosis still remains uncertain, then a surgeon may perform an excisional lymph node biopsy to remove the suspicious lump under general anaesthesia and send the sample to the pathologist for review. 


This is used to create a picture of the tissues in the neck, and is a very good way to assess the thyroid gland.


This uses X-rays to take pictures of the inside of the body. Depending on the clinical situation, patients may require a CT scan of the head, neck, and possibly the chest. Often dye is injected into a vein during the procedure to give clearer images.

MRI (Magnetic Resonance Imaging) scan

This uses magnetic fields to take pictures of the inside of the body, however this is less commonly used than CT scans.


As the cancerous lymph nodes are often too small to detect, PET scan is unable to show the cancer in the lymph nodes. However, using a radioactive form of sugar, PET shows if the cancer has spread elsewhere in the body and could help identify where the cancer has come from (the primary site).


This is part of the dental assessment, which may be needed before treatments.

All the information in this section is available in a PDF.
Download it here.
  • What is Cancer of Unknown Primary?
  • What are Lymph Nodes?
  • What causes Cancer of Unknown Primary?
  • Signs and Symptoms of Cancer of an Unknown Primary
  • Tests for Cancer of an Unknown Primary?
  • Treatment options for Cancer of Unknown Primary
  • Surgery 
  • Radiation Therapy
  • Chemotherapy
  1. Head and Neck Cancer Australia Resources 
  2. External Links to other Head and Neck Cancer Resources