Carcinoma of Unknown Primary Health Article

Definition

Carcinoma of unknown primary (CUP) is a disease in which malignant (cancerous) cells are found in the body, but the organ where they initially began growing, the primary site, cannot be discovered.

Description

The area where a cancer originates in the body is often referred to as the primary tumor. Cancer of unknown primary is a cancer that starts out in an unknown spot and then metastasizes (spreads) to another site, such as a lymph node, the liver, lung, brain, or the bones. Because the primary site is unknown, prognosis may differ from patient to patient.

Most cancers are named after the area of the body in which they start. For example, breast cancer is cancer that originates in the breast. If it spreads to another part of the body, it is still called breast cancer, and the cancerous cells that have metastasized still look like breast cancer cells. With CUP, however, doctors are unable to know with certainty the origin of these cells.

Demographics

According to the American Cancer Society, about 35, 000 cases of cancer of unknown primary are diagnosed each year. These represent approximately 3% to 5% of all cases of cancer. The average age of a patient diagnosed with CUP is approximately 58. The disease is more common in men than in women.

Causes and symptoms

Every cancer has distinct risk factors, or causes. It is difficult to identify specific causes of CUP since the exact type of cancer is unknown.

The symptoms of carcinoma of unknown primary are organ-specific. These symptoms may include:

• Lymphadenopathy, a condition in which the lymph nodes are swollen, firm to the touch, but do not hurt. Cancers frequently spread to the lymph nodes.
• A mass in the abdomen or a feeling of abdominal fullness. This is often caused by a cancer growing in the liver or the spleen, or by a collection of fluid inside the abdomen called ascites.
• Shortness of breath. This symptom may be caused by cancer that has spread to the lungs or from pleural effusion, a build-up of fluid and cancer cells in the area around the lungs.
• Pain in the chest or abdomen. Cancer growth around nerves or tumors pressing against internal organs may cause these symptoms.
• Bone pain. Severe pain may occur when cancer has spread to the bones. Bones that are made weak by the cancer's spread may contribute to fractures. These fractures may result from minor injuries, or even from normal activities, like rolling over in bed.
• Skin tumors. Some cancers start out in organs and spread through the bloodstream to the skin. Skin metastases are sometimes the first sign of spread from a cancer of unknown primary.
• Weakness, fatigue, poor appetite, and weight loss. These generalized symptoms may happen because the cancer has spread to specific organs or systems. Also, some cancers release hormone-like substances into the bloodstream that affect metabolism and cause these same problems.