Cancer of Unknown Primary - What is it?

by Jane Ashley

Imagine finding out that you have cancer, but the medical team doesn’t know where the cancer began.

What Is Cup

How is Cancer of Unknown Primary (CUP) Discovered?

It depends on the circumstances. Sometimes, CUP is accidentally found during surgery for something else or through a scan given for another reason.

A nodule might show in a CT scan of the lung when trying to determine if a patient has pneumonia.

• A person might fall and hit their head requiring stitches at the ER — the ER physician orders a CT scan of the head to ensure that the patient doesn’t have a brain bleed. In turn, the CT scan shows a nodule in the patient’s brain.

• A person may detect a swollen lymph node in their neck while showering.

Accidental discoveries of nodules and swollen lymph nodes lead to more tests and a biopsy.

Suppose that a biopsy is performed on the lymph node that is removed, but the cancer cells don’t resemble a kind of cancer that starts in the lymph nodes. Instead, they look like cancerous cells that begin in the larynx (voice box). The larynx is examined — if a cancerous tumor is found, then the patient is diagnosed with larynx cancer. But if examinations, tests, and scans are negative, then the patient is said to have a cancer of unknown primary.

Cancer Of Unknown Primary Newsletter

How is Cancer of Unknown Primary Diagnosed?

A physician will conduct a comprehensive interview with the patient, probing for symptoms. Men should get a prostate exam, and women should get a breast and pelvic exam — since these are commonly diagnosed cancers. Blood tests may be ordered looking for abnormalities.

The pathologist who performs the biopsy hopes to identify the cells by their unique shape and characteristics. There are four types of cancer cells. Process of elimination usually helps identify what kind of cancer a patient has so the patient can be successfully treated.

Adenocarcinoma. This type of cancer accounts for 6 out of every 10 cases of cancer. These are usually breast, colorectal, esophageal, lung, ovarian, pancreatic, prostate or stomach cancers. Blood tests like PSA for prostate of CEA for colorectal cancers give the medical team other clues. A PET scan may also reveal the location of the original tumor.

Neuroendocrine carcinoma. This type of cancer may be low-grade or high-grade. They can occur in many places — lung, bowel, pancreas, appendix, liver, gallbladder, adrenal gland, kidney, pituitary gland, thyroid and parathyroid. Scans, blood work and urine tests help physicians track down the location of low-grade neuroendocrine carcinomas. High-grade neuroendocrine cancers are more aggressive and may spread to multiple sites within the body. MRI and CT/PET scans examine the chest, abdomen and pelvis.

Squamous cell carcinoma. These cancers occur in the head and neck, lung, skin, cervix, vagina, vulva and anus. The location of swollen lymph nodes can usually predict the type of squamous cell carcinoma.

Poorly differentiated tumors. These cancers account for 3 out of 10 cancers. They are more difficult to diagnose. Poorly differentiated tumors are sometimes a germ cell cancer, melanoma, lymphoma or sarcoma. Imaging and specific blood tests help point physicians to a definite diagnosis.

Diagnosing cancer of unknown primary is kind of like working backward to find the source. Eventually, your medical team will learn enough about the source of the original cancer to treat you. But they may never find the original tumor.

An Introduction to Cancer Of Unknown Primary

How is Cancer of Unknown Primary Treated?

Treatments include all of the normally approved cancer treatments — chemotherapy, radiation, and surgery. Sometimes, in the course of surgery, the primary tumor is found.

If the original location is found and the type of cancer is determined, treatment will be the recommended treatment for that kind of cancer.

If the origin of the primary is never found, treatment is based on what it is most likely to be.

• Squamous cells in the lymph nodes in the neck – most likely to be a cancer in the mouth, throat or larynx.

• Adenocarcinoma in lymph nodes under the arm – most likely to be breast cancer.

• Cancerous lymph nodes in the groin – doctors delve into trying to determine the location of these cancers as many of them can be treated if found.

• Women with cancer throughout the pelvic region – even though the original tumor site is not found, almost all of these cancers are ovarian or similar to ovarian and treated as ovarian cancer.

Unfortunately, there is a subset of patients where the primary location cannot be determined. These patients usually have cancer in their bones, liver or lungs. Oncologists treat these cancers of unknown primary with a standard chemotherapy regimen that works well for many patients.

Patients with no definitive answers would be well served to seek a second opinion from a National Cancer Institute-designated hospital. These larger cancer centers are more likely to have experience with this rare subset of patients. About 2 percent of patients in the U.S. are diagnosed with CUP annually.

More specific blood assays (for genetic mutations and specific markers) offer hope for patients who don’t have a specific diagnosis.

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