Cancer Staging

Classification of cancer determines appropriate treatment and helps determine the prognosis. Cancer develops progressively from an alteration in a cell's genetic structure. This change (mutation) results in cells with uncontrolled growth patterns. Cancer classification is made according to the site of origin of the malignant cells; the histology, or cell analysis (called grading); and the extent of the disease (called staging).

Site of Cancer Origin

This classification describes the type of tissue in which the cancer cells begin to develop.

Here are some common examples of site of origin classification:

  • Adenocarcinoma–originates in glandular tissue
  • Blastoma–originates in embryonic tissue of organs
  • Carcinoma–originates in epithelial tissue (i.e., tissue that lines organs and tubes)
  • Leukemia–originates in tissues that form blood cells
  • Lymphoma–originates in lymphatic tissue
  • Myeloma–originates in bone marrow
  • Sarcoma–originates in connective or supportive tissue (e.g., bone, cartilage, muscle)

Tumor Grading

Grading involves examining tumor cells that have been obtained through biopsy under a microscope. The abnormality of the cells determines the grade of the cancer. Increasing abnormality increases the grade, from 1–4. Cells that are well differentiated closely resemble mature, specialized cells. Cells that are undifferentiated are highly abnormal, that is, immature and primitive.

    Grade 1 Cells slightly abnormal and well differentiated
    Grade 2 Cells more abnormal and moderately differentiated
    Grade 3 Cells very abnormal and poorly differentiated
    Grade 4 Cells immature and undifferentiated

Cancer Staging

Staging is the classification of the extent of the disease. There are several types of staging methods. The tumor, node, metastases (TNM) system classifies cancer by tumor size (T), the degree of regional spread or node involvement (N), and distant metastasis (M).

Tumor (T)

    No evidence of tumor
    Tis Carcinoma in situ (limited to surface cells)
    T1-4 Increasing tumor size and involvement

Node (N)

    N0 No lymph node involvement
    N1-4 Increasing degrees of lymph node involvement
    Nx Lymph node involvement cannot be assessed

Metastases (M)

    M0 No evidence of distant metastases
    M1 Evidence of distant metastases

A numerical system also is used to classify the extent of disease.

    Stage 0 Cancer in situ (limited to surface cells)
    Stage I Cancer limited to the tissue of origin, evidence of tumor growth
    Stage II Limited local spread of cancerous cells
    Stage III Extensive local and regional spread
    Stage IV Distant metastasis

Publication Review By: the Editorial Staff at

Published: 01 Sep 2002

Last Modified: 04 Nov 2014