Secondary cancer is metastatic cancer that has spread from another part of the body. It's different from primary cancer, which is cancer that has originated in the location where it was diagnosed. When cancer originates in one part of the body, and then spreads to another part, the cancer that appears in the new locations is generally known as secondary cancer. It is therefore possible to have both primary and secondary cancer at the same time.
There are believed to be more than 200 kinds of cancer. Each one generally originates in a different point in the body, and may spread to another point via the process known as metastasis. The speed and likelihood of metastasis often depends on the type of cancer involved.
Most cancers spread through the lymphatic system or the bloodstream. The lymphatic system is the system that produces immune cells and is responsible for helping the body fight infection. Lymph nodes and lymph channels throughout the body distribute lymph, a fluid that removes unwanted materials, including bacteria, from the bloodstream. When cancer affects the lymph nodes, or the bone marrow where blood cells are produced, it can spread quickly throughout the body.
Even though cancer may spread from its point of origin, it remains the same type of cancer even when it takes hold in the new location. If cancer originates in the lungs, for instance, and then spreads to the stomach, the new tumor in the stomach is made up of cancerous lung cells just like those in the first tumor. Therefore, the new cancer would be considered secondary lung cancer of the stomach, not stomach cancer.
Treating secondary cancer is often more difficult than treating primary cancer. When a diagnosis of primary cancer is made, that usually means that cancer has not yet spread from its point of origin. Cancer that has not yet spread beyond its point of origin can often be surgically removed. Even if complete surgical removal is not possible, treatments such as chemotherapy and radiation therapy can reduce or eliminate the tumor, stop its growth, or keep it from coming back after surgical removal.
Once cancer has spread and become secondary cancer in another part of the body, surgical removal of tumors becomes more difficult. If cancer has affected the lymphatic system or has entered the bloodstream, it may have spread to multiple organs in the body. Cancerous tumors may develop practically anywhere in the body, including the muscles, bones, lymph nodes, bone marrow, reproductive organs, spine, and brain. Once secondary cancer has developed, the prognosis can become very poor.