CUP, also known as Cancer of unknown primary, is Cancer that has metastasized from another body part. The site where it began, also called the primary site, is unknown in this case.

Why CUP is a challenging cancer?

Cancer of unknown primary is often challenging because it tends to be aggressive and spreads to many body parts when found. Only 2 to 5% of CUP cancers are diagnosed in the U.S. In addition, because the origin of this type of Cancer is unknown, it often is challenging to choose the best treatment. CUPs are usually found in the lymph nodes, liver, lung, peritoneum (lining of the bowel), or bone, and thanks to better diagnostics and screening, they are becoming less common nowadays.

What are the primary causes?

Because the primary site of many of these cancers is unknown, it is hard to predict the primary cause. Even in cases where the primary location is found, the type of Cancer determines the possible risk factors.

Types of CUP cancers

Even when an Oncologists is unable to determine the initial site where the Cancer began, A further microscopic inspection of the cancer cells concludes the Cancer falling into one of the following categories:

• Neuroendocrine carcinoma: These are cancers that begin in specialized cells called neuroendocrine cells and have traits similar to those of nerve cells and hormone-producing cells. Neuroendocrine tumors are rare and can occur anywhere in the body. Most of this happens in the lungs, appendix, small intestine, rectum, and pancreas.
• Poorly differentiated carcinoma: Cancer cells are present in this type of CUP, but they do not have enough detail for an oncologist to decide the type of Cancer. Around 10% of these CUP cases are lymphoma, melanoma, or sarcoma.
• Adenocarcinomas: In six of every ten cancers of unknown primary are adenocarcinomas, beginning in gland cells, with the primary sites in the lung, pancreas, breast, prostate, stomach, liver, or colon.
• Squamous cell cancer: These cells are flat, similar to cells on the skin or linings of some organs

What are the Symptoms of Cancer of Unknown Primary?

While the Symptoms of Cancer of unknown primary (CUP) vary from person to person and depend on where Cancer has spread, patients often experience it.

• Swollen lymph nodes that are not painful but firm.
• Abdominal Mass that can be felt from the outside, often causing a feeling of fullness after a small meal
• Shortness of breath
• Pain in the chest or abdomen
• Pain in the bones
• Skin tumors
• Fatigue or weakness
• Lack of appetite or unexplained weight loss

How is CUP Diagnosed?

If an oncologist suspects Cancer of unknown primary, one or more of the following tests may be performed for an accurate diagnosis.

1. Biopsy
   1. Fine needle aspiration (FNA)
   2. Core needle biopsy
   3. Excisional biopsy
   4. Incisional biopsy
   5. Bone marrow aspiration and biopsy
2. Blood and urine tests
3. Imaging tests, which may include
   1. X-rays
   2. CT or CAT computed axial tomography) scans
   3. MRI (magnetic resonance imaging) scans
   4. Ultrasound
   5. PET (positron emission tomography) scans
4. Endoscopy
5. Colonoscopy

What are the available Treatments?

• Surgery
• Chemotherapy
• Radiation therapy
• Brachytherapy
• 3D-conformal radiation therapy
• Intensity-modulated radiotherapy (IMRT)
• Proton therapy
• Targeted therapies

Finally, Cancer of unknown primary is rare, and it’s essential to be aware of the symptoms and see a doctor immediately if you experience any of them. With early diagnosis and treatment, many people with this type of Cancer can beat the disease successfully.