Cancer of unknown primary (CUP) is a diagnosis given when a cancerous tumour has spread (metastasised) from its original site to another part of the body, but the initial location, or primary site, cannot be identified.
Although CUP cases account for a small percentage (around 2% to 5%) of all cancer diagnoses, advancements in diagnostic testing are making this diagnosis less common. In fact, for approximately four out of every five cases initially diagnosed as CUP, the specific type of cancer is eventually confirmed.
CUP is often found in the:
Cancer of unknown primary can be particularly challenging because it tends to be aggressive and may have spread significantly before detection. The inability to pinpoint the cancer's origin can also complicate the selection of the most effective, tailored treatment plan.
While the primary source is initially unknown, doctors study the cancer cells to categorise the type. After microscopic examination, CUP usually falls into one of the following categories:
Approximately six out of every ten CUP cases are adenocarcinomas, meaning the cancer began in glandular cells. The most common primary sites for these types of cancers include the lung, pancreas, breast, prostate, stomach, liver, or colon.
Cancer cells are present but lack enough detail for doctors to definitively classify the type of cancer. Around 10% of these cases are later identified as lymphoma, melanoma, or sarcoma.
The cancer cells are flat, similar to the cells found on the surface of the skin or the linings of certain internal organs.
The cells are clearly cancerous, but they are so abnormal that their cell type or original location in the body cannot be determined. These can sometimes be lymphomas, sarcomas, or melanomas.
This type of CUP originates in the neuroendocrine system, giving the cells characteristics similar to both nerve cells and hormone-producing cells. These cells are scattered throughout organs such as the oesophagus, stomach, pancreas, intestines, and lungs.
Since the primary site is often not found, determining the exact cause of CUP can be difficult. For cases where the primary site is eventually identified, potential risk factors are based on that specific cancer type:
Tobacco use is a risk factor for cancers of the pancreas, lungs, kidney, throat, larynx, and oesophagus. More than half of people with CUP have a history of tobacco use.
Being overweight or having an unhealthy diet is linked to cancers that start in the stomach, colon, or rectum.
Excessive sun exposure is a cause of some melanomas.
It is important to note that a direct causal link between these factors and the development of cancer of unknown primary has not been conclusively proven.
The symptoms of cancer of unknown primary (CUP) vary widely among individuals, depending on where the cancer has spread within the body. They may include:
It is essential to remember that these symptoms do not automatically indicate CUP; they may be signs of other health conditions. You should always discuss any concerning symptoms with your doctor.
Thanks to new scientific advancements, doctors are increasingly successful at finding the origin of CUP. The primary site can now be determined in approximately four out of five cases originally diagnosed as CUP.
Clues that help determine the primary site include:
The initial location where cancer cells are found
The pattern in which the cancer cells are spreading
The specific type of cell present in the remote cancer
The first step in diagnosing CUP is a comprehensive patient history and physical examination. The doctor will ask about your current and past health, as well as risk factors such as smoking habits or family history of cancer.
If cancer of unknown primary is suspected, one or more of the following tests may be conducted:
Various biopsy methods are used based on the location and type of cancer:
A thin needle is used to draw out cells for examination under a microscope.
Similar to FNA but uses a slightly larger needle to remove a bigger piece of tissue, often providing more diagnostic information.
The entire tumour or swollen lymph node is surgically removed.
Only a part of the tumour or lymph node is surgically removed.
A long, hollow needle is used to collect a small sample of fluid, typically used if there is a significant fluid build-up in the abdomen or lungs.
A small sample of bone marrow (liquid from the centre of large bones) is withdrawn using a needle inserted into the hip bone.
Blood and urine tests
Imaging tests, which may include:
Endoscopy: A flexible tube (endoscope) is inserted through the mouth, nose, or anus, or sometimes through a small cut in the skin, depending on the location of the cancer.
Colonoscopy
Unlike other cancers, CUP cannot be staged using standard methods because the primary origin is unknown. Instead, doctors make predictions about the prognosis and determine treatment based on:
Where the cancer has spread
The appearance of the cancer cells under a microscope
How well the cancer responds to initial treatment
Your overall general health
Your treatment at SSCHRC for cancer of unknown primary (CUP) is highly personalised to provide the most effective options while minimising the impact on your body. As a leading centre, SSCHRC has significant experience in managing CUP patients, which is crucial for achieving a successful outcome.
Since every patient and every CUP is unique, your treatment will be carefully tailored to your individual needs. A collaborative team approach ensures that you receive optimal care from the brightest minds.
If you are diagnosed with CUP, your doctor will discuss the best treatment options with you. Several factors are considered, including:
Extent: The number and size of the cancerous areas affected by the CUP tumour.
Site: Which organs are involved (e.g., lymph nodes, liver, lungs, bones).
Your general health.
Your customised treatment plan may include one or more of the following therapies to treat the cancer or to help relieve symptoms:
May be used if the cancer is confined to a single area, such as a lymph node or one organ. The type of surgery performed depends on the CUP's location. Surgery may be combined with chemotherapy or radiation therapy.
SSCHRC provides the most advanced and up-to-date chemotherapy options for CUP.
SSCHRC offers the latest radiation treatments, including:
Tiny radioactive seeds are placed directly into the body near the tumour.
Multiple radiation beams are precisely shaped to match the tumour's exact shape.
Treatment is meticulously tailored to the specific contours of the tumour.
SSCHRC is among a select few cancer centres able to offer targeted therapies for some types of cancer of unknown primary. These innovative drugs work by interfering with specific proteins, receptors, or blood vessels that the tumour relies on for growth.