Grading and staging systems

Tumor grading

Evaluation of the maturity and differentiation of tumor cells under a microscope

Grade I tumor

Well-differentiated tumor that closely resembles normal cells

Grade II tumor

Tumor with an intermediate degree of differentiation

Grade III tumor

Moderately to poorly differentiated tumor

Grade IV tumor

Very poorly differentiated or undifferentiated tumor

Tumor staging

Evaluation of the extent of tumor spread in the body

TNM system

Staging system based on tumor, regional lymph nodes, and distant metastasis

T in TNM

Tumor size and degree of local extension

N in TNM

Regional lymph nodes involved by tumor cells

M in TNM

Spread of tumor cells to distant sites

Stage I

Generally a small tumor without spread to regional lymph nodes or distant sites

Stage II

A more advanced stage that may include regional lymph node involvement

Stage IV

Stage that includes distant metastasis

Prognosis

Expected outcome or course of a disease

CT scan in staging

Imaging used to assess tumor size and spread

PET-CT

Combined imaging used to help assess tumor spread

MRI in staging

Imaging used to assess tumor extent and possible spread

Radionuclide bone scan

Imaging used to assess possible spread to bones