Tumor stage is usually the most important prognostic factor in determining a patient's outcome. Staging typically involves ordering appropriate tests to identify the local extent of the primary tumor and to determine whether the disease has spread beyond the site of origin. Although specific staging will vary according to the unique anatomic and biologic features of the primary site, there are many common steps to the staging process. Most solid tumors are staged according to the American Joint Commission on Cancer (AJCC) TNM classification. “T” indicates the extent of the tumor (size and/or depth of penetration), “N” represents the number of locoregional lymph nodes that contain cancer, and “M” indicates whether metastases are present or absent. TNM scores are then classified on a scale of stage I to IV, with stage I tumors having the best prognosis and stage IV having the worst.

Although poorly differentiated tumors generally have a worse prognosis than well-differentiated tumors, this is a modest prognostic factor compared with staging.

Performance status, which is a designation of the patient's overall medical “wellness” and ability to perform routine daily activities, may have important prognostic implications within a particular stage of disease but is far less significant prognostically than the stage itself.

Tumor size may be a component of the “T” stage, but by itself has only modest prognostic significance relative to overall stage. Generally, the degree of lymph node involvement has a greater negative impact on prognosis than does a higher T stage, and the presence of metastatic disease beyond lymph node involvement has the worst prognosis.