There are various stages of cancer, and some terms in regards to the different stages of cancer vary, and are also used interchangeably. After it has been confirmed that a cancer really exists, the degree to which the cancer has developed is determined. The most important reason is providing a universally understood definition of a particular cancer progress. It helps in planning the treatment protocol for that particular cancer, determining prognosis, and also allows accurate end-results reporting.
Stage 0: The malignant cells are present as a tumor but has not metastasized, or invaded, beyond the original site where the tumor was discovered. This is called “Carcinoma In Situ".
Stage I: The cancers are small and localized to one part of the body. The cancers at this stage are not advanced and are usually easily curable.
Stage II: The cancers are locally advanced within the affected body part.
Stage III: The cancers are also locally advanced, and underlying lymph nodes and tissues are also affected along with the organ. Whether a cancer is designated as Stage II or Stage III can depend on the specific type of cancer; for example, in Hodgkin's disease, Stage II indicates affected lymph nodes on only one side of the diaphragm, whereas Stage III indicates affected lymph nodes above and below the diaphragm. The specific criteria for Stages II and III therefore differ according to diagnosis.
Stage IV: The cancers have often metastasized, or spread to other organs or throughout the body.
For solid tumors, stages I-IV are defined in a more detailed staging system called the "TNM" system, which stands for Tumor, Nodes, and Metastases. Within the TNM system, a cancer may also be designated as recurrent, local or distant. T classifies the extent of the primary tumor, and is normally given as T0 through T4. N classifies the amount of regional lymph node involvement, and is normally given as N0 through N4. M is either M0 if there are no metastases or M1 if there are metastases.
There are no set rules that state all cancers are best classified into just four prognostic groups. For many cancers four prognostic groups is not enough, so the overall staging is further distinguished with classifications like IIa, and IIIb. In addition, prostate and colon cancer are sometimes staged as A through D rather than I through IV. Finding the specific staging and prognostic information is imperative to know for each individual case.
How does Cancer Spread?
The three ways that cancer spreads in the body are through the bloodstream, tissues, and lymph system. As with healthy cells, all cancer cells must have a blood supply in order to live, so mainly all cancer cells have access to the bloodstream. The cancer basically invades the veins and capillaries, and travels through the blood to other places in the body. Cancers that spread to healthy tissues normally do not venture very far from the original location. The most common way for cancer to spread is through the lymphatic system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
When cancer cells break away from the primary tumor and travel through the lymph or blood to other places in the body, a secondary tumor may develop. This process is called metastasis. A cancer which has spread to other organs is called metastatic. The secondary tumor is the same type of cancer as the primary tumor. For example, if lung cancer spreads to the bones, the cancer cells in the bones are actually lung cancer cells. The disease is metastatic lung cancer, not bone cancer.
Recurrence of Cancer
It is common for cancer to return months or years after the primary tumor has been removed. The tumor returns because by the time the primary tumor was discovered cancer cells had already broke away and lodged in to distant locations. Cancers that reappear after being in remission or after all visible tumors were removed is called recurrent disease. Cancer that recurs in the area of the primary tumor is referred to as locally recurrent, and cancer that recurs as metastases, meaning that it appears in a different part of the body, is referred to as a distant recurrence.