Classification

• Classification of cancer is done by

  • anatomical site
  • histological analysis grading severity
  • classifying extent of disease staging
• Classification systems provide a standardized way to

  • communicate with the health care team
  • prepare and evaluate treatment plan
  • determine prognosis
  • compare groups statistically
• Cancer cells are identified by tissue of origin, anatomical site and behaviours of tumour (benign vs malignant)
• Anatomical site

  • carcinomas originate from skin, glands, mucous membranes of resp, GI and Gu tracts
  • sarcomas originate from connective tissue, muscle, blood vessels, nerves, bone, cartilage, fat
  • lymphomas and leukemias originate from hematopoitic system
• Histological analysis

  • Grade 1: cells differ slightly from normal cells but are still well differentiated
  • Grade 2: cells are more abnormal, moderately differentiated
  • Grade 3: cells are very abnormal, poorly differentiated
  • Grade 4: immature and primitive cells, undifferentiated, origin cell is hard to determine
• Histological classification: appearance of cells and degree of differentiation are evaluated to determine how closely cells ressemble tissue of origin
• Poorly differentiated or undifferentiated tumours have a worse prognosis than those closer in appearance to normal cells
• Clinical staging: description of the extent of the disease rather than on cell appearance. It is important for prognosis
• Clinical staging

  • Stage 0: cancer in situ (neoplastic cells are found)
  • Stage 1: Tumor is limited to tissue of origin, localized
  • Stage 2: limited local spread
  • Stage 3: extensive local and regional spread
  • Stage 4: metastasis
• The TNM classification system determine the extent of disease process of cancer according to

  • tumour size and invasiveness
  • spread to lymph nodes
  • metastasis
• TNM: tumour size

  • T0: no evidence of primary tumour
  • Tis: carcinoma in situ
  • T1-T4: ascending degrees of increase in tumour size and involvement
  • Tx: primary tumour cannot be assessed
• TNM: involvement of lymph nodes:

  • N0: no evidence of disease in lymph nodes
  • N1-N3: ascending degrees of nodal involvement
  • Nx: regional lymph nodes cannot be assessed
• TNM: metastasis

  M0: no distant metastases

  M1: distant metastases

  M2: distant metastases cannot be assessed