Classification of cancer

Tumors can be classified by
- Anatomic site
- Histology
  - Grading severity
- Extent of disease
  - Staging
Classification systems provide a standardized way to
- Communicate with health care team
- Prepare and evaluate treatment plan
- Determine prognosis
- Compare groups statistically
Anatomic site classification
- Identified by tissue of origin
- Carcinomas originate from
  - Embryonal ectoderm (skin, glands)
  - Endoderm (mucous membrane of respiratory tract, GI and GU tracts)
- Sarcomas originate from
  - Embryonal mesoderm (connective tissue, muscle, bone, and fat)
- Lymphomas and leukemias originate from
  - Hematopoietic system
Four grades of abnormal cells
- Grade I
  - Tumor limited to tissue of origin; localized tumor growth
- Grade II
  - Limited local spread
- Grade III
  - Extensive local and regional spread
- Grade IV
  - Cells are immature and primitive and undifferentiated
  - Cell of origin is difficult to determine
  - Metastasis
TNM classification system
- Anatomic extent of disease is based on 3 parameters:
  - Tumor size and invasiveness (T)
  - Spread to lymph nodes (N)
  - Metastasis (M)
Staging
- Performed initially and at several evaluation points
  - Clinical staging
    - Done at completion of diagnostic workup to guide effective treatment selection
      - Bone and liver scans, ultrasonography, CT, MRI, PET scans
  - Surgical staging
    - Determined by surgical excision, exploration, and/or lymph node sampling
    - Exploratory surgical staging is being used less frequently

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