When cancer has been diagnosed, the physician will order additional tests, such as a biopsy or imaging studies, to reveal whether or not the cancer has spread (metastasized). This process is known as staging, and it is used to help determine the most effective treatment plan and the patient's prognosis.

The prognosis (predicted outlook or chance of survival) of esophageal cancer depends on the cancer’s stage and grade. The stage indicates the extent of the cancer, or how widespread it is in the body. The grade measures how abnormal the cells look under a microscope. The grading and staging systems are combined into another system that allows the physician to discuss the pathology in layman’s terms. 

There are a variety of systems used for staging cancers. The TNM system of the American Joint Committee on Cancer (AJCC) is the most commonly used staging system. It is based on three important factors:

• T describes the original (primary) tumor (e.g., size, location).
  
  
• N describes whether or not the cancer has spread to neighboring lymph nodes.
  
  
• M describes whether or not there are distant metastases (spread of cancer to distant parts of the body).

Sometimes, additional letters will follow the T, N or M, such as “Tm,” which indicates the presence of multiple cancers or “Tis,” which indicates that the cancer is superficial (carcinoma in situ) and has not invaded surrounding tissues.

The stages of esophageal cancer are:

• Stage 0. Cancer is found only in the most superficial layer of cells lining the esophagus and is not capable of invading other parts of the body at present. Nonetheless, they should be removed or monitored closely to ensure they do not eventually become invasive.
  
  
• Stage I. Cancer has spread to the next layer of tissue in the wall of the esophagus.
  
  
• Stage II. Cancer has invaded deeper layers of the esophageal lining such as the esophageal muscle or the outer wall of the esophagus. Cancer may also have spread to nearby lymph nodes.
  
  
• Stage III. Cancer has spread more deeply into the outer esophageal wall and to nearby tissues or lymph nodes.
  
  
• Stage IV. Cancer has spread to other parts of the body, such as distant lymph nodes and organs.