Cancers of unknown primary (CUP), also known as cancers of occult primary, are a type of cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs that has spread from an unknown point of origin. It is known as a secondary or metastatic cancer (cancer that has spread from another part of the body), and the primary cancer it originated from cannot be located. As it is a secondary cancercancer that has spread from another part of the body, also known as metastasis or mets, patients with CUP often present at an advancedat a late stage, far along stage of disease.
There are many reasons that a primary cancer can’t be located, such as the primary cancer is too small to be detected, the immune system has already killed the primary cancer, the primary cancer may have been removed during surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence for another condition, or the primary cancer is hidden by a larger secondary cancer nearby. While it is helpful to know where the primary cancer is located, the doctors can perform tests on the secondary cancer to determine what it most likely is, and how to treat it.
CUP is generally found equally among the sexes, and is most likely to be found in people over 60 years old. However, anyone can develop this disease.
Types of CUP
Although the primary cancer cannot be located, doctors can perform tests on the secondary cancer to determine the type of cellsthe basic structural and functional unit of all living things the cancer originated from. In most cases of CUP, the patient has a type of carcinomacancer arising from tissues that line organs (cancer arising from epithelial cells and tissues that line organs). There are many different types of carcinomas, which are categorised by the type of epithelial cell they develop from.
Adenocarcinoma
Adenocarcinomas are cancers that arise from mucus-producing glands in organs, and is the most common type of cancer cell found in patients with CUP. They generally have primary cancers originating in the lungs, liver, stomach, pancreasa long, flat organ that sits between the stomach and the spine that plays a key role in digestion and blood sugar regulation, bowelportion of the digestive system that digests food (small bowel) and absorbs salts and water (large bowel); also called intestines, and/or prostatea walnut-shaped gland in the male reproductive system that is responsible for producing semen - a bodily fluid that acts as a vessel for sperm transport during ejaculation, but could potentially start in other parts of the body as well.
Poorly Differentiated Carcinoma
Poorly differentiated carcinomas are cancer cells that have enough detail for a doctor to determine that they are a carcinoma by examining them under the microscope, but they cannot determine what type of carcinoma the cancer is. They are the second most common type of cancer cell found in patients with CUP, and generally don’t provide enough information to suggest where the primary cancer is located.
Squamous Cell Carcinoma (SCC)
Squamous cell carcinomas (SCCs) are cancers that arise from squamous cells, which form the surface layer of the skin and the lining of hollow organs, the respiratory tract, and the digestive tract. They generally have primary cancers originating in the head and neck area, oesophagus, lungs, pancreas, cervix, vagina, or skin, but could potentially start in other parts of the body as well.
Rare types of CUP
These types of CUP are considered rare:
- Neuroendocrine tumours (a type of malignancy that often produce hormones and may be located in the gastrointestinal tract or pancreas).
- Undifferentiated neoplasms (cells that can be determined as a cancer, but cannot determine what type of cancer they are).
- Metastatic neck cancer with occult primary.
Treatment
When cancers are detected, they are staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancer cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you. However, as CUP is a disease with an unknown primary cancer, there is currently no standard staging and grading system for this disease. Instead of staging and grading, your doctor will recommend a treatment plan based on the following factors:
- Your age.
- General health.
- The location of the secondary cancer.
- Where the primary cancer is suspected to be located.
- Diagnostic test results.
- What will give you the best outcome.
- Your treatment preferences.
Your doctor may also recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumoura tissue mass that forms from groups of unhealthy cells DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment for CUP may include:
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Hormone therapymedication that alters the levels of certain hormones in the body, such as oestrogen and progesterone.
- Targeted therapymedication that targets specific molecular features of cancer cells.
- Immunotherapya treatment that uses a person's immune system to fight cancer.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Surgery (generally to remove as much of the cancer as possible).
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
Each case of CUP will have different riskthe possibility that something bad will happen factors, depending on the type of primary and secondary cancer you have. As each different cancer has a different set of risk factors, it is difficult to determine definitive risk factors of CUP.
Generic factors that may increase the risk of developing cancer may include:
- Older age.
- Having an unhealthy diet.
- Having a history of drinking.
- Having a history of smoking.
- Family history.
- Being overweight.
- Having certain infections.
- Not getting enough exercise.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Symptoms
Each case of CUP will have different symptoms, depending on the type of primary and secondary cancer you have. As each different cancer has a different set of symptoms, it is difficult to determine definitive symptoms of CUP.
Generic symptoms that may be indicative of cancer include:
- Fatiguea state of extreme tiredness or exhaustion, can be physical or mental.
- Unexplained weight loss/loss of appetite.
- Nauseato feel sick or likely to vomit and/or vomiting.
- Dyspneadifficulty breathing, shortness of breath.
- Discomfort in the chest area.
- Persistent cough.
- Pain in the bones, back, head, abdomenstomach, stomach area, belly, or other areas.
- Swelling or bloating of the abdomen.
- Changes in bowel habits, potentially including:
- Constipationa condition where a person has difficulty passing faeces/stools.
- Diarrhoeafrequent discharge of watery or loose stools from the body.
- Jaundiceyellowing of the skin and the whites of the eyes.
- Lymphadenopathyswollen lymph nodes/glands, also known as adenopathy, most commonly in the underarm, chest, and/or groinarea between the abdomen and thighs.
Not everyone with the symptoms above will have cancer, but see your GP if you are concerned.
Diagnosis
If your doctor suspects you have CUP, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Urine teststesting done to measure the levels of certain substances in the urine.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- PET (positron emission tomography) scana type of medical imaging that uses radioactive tracers to create detailed images of the body.
- X-raya type of medical imaging that uses x-ray beams to create detailed images of the body .
- Ultrasounda type of medical imaging that uses soundwaves to create detailed images of the body .
- Exploratory surgeryan exploratory surgical procedure used for conditions that cannot be confirmed by scans and tests alone.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
