After the primary site of the tumor has been identified, almost every tumor can be further classified into subtypes, both clinically and pathologically. The clinical stage of the tumor classifies the extent of the neoplasm. The TNM staging system is the most common; under this system, staging is determined from three factors:

• The size of the tumor (T)
• The involvement of nearby lymph nodes (N)
• The metastasis of the tumor to other bodily sites (M)

Usually, survival rates are given depending on the clinical stage, which in turn is determined by the TNM staging criteria, which differs for each tumor.

The pathologic grade of the tumor concerns the cellular characteristics of its cells. Things that pathologists look for when setting a tumor grade include the similarity of tumor cell appearance to normal cell appearance (differentiation) and the existence of normal cell organelles (National Cancer Institute, 2015).