Neoplasia I

Basic definitions

  • Cancer: uncontrolled cell proliferation and growth that can invade other tissues
  • Tumour: swelling, can be benign or malignant
    • Could even be inflammatory or a foreign body
  • Neoplasia: new growth which is not in response to a stimulus
    • Can be benign, premalignant or malignant
    • Can occur in any cell in any organ

Malignancy

  • Metastatic potential: can spread to other sites (metastases)
  • In epithelium, malignancy goes beyond the basement membrane - invasion
    • Access to blood vessels, lymph nodes etc.
  • Not quite binary - precursor stages (dysplasia, metaplasia)

Dysplasia

  • Dysplasia: abnormal cells growing without a stimulus
  • No invasion
  • Often graded – higher grades have a high risk of developing malignancy

Carcinoma in-situ (CIS)

  • Dysplasia affecting whole of epithelium
  • Last stage before becoming malignant

Metaplasia

  • Metaplasia: reversible change from one mature cell type to another mature cell type
  • Due to a change in the demand placed on the tissue
    • Commonly due to a noxious stimulus
    • Squamous epithelium covers skin and is very resistant to a range of noxious stimuli - metaplasia often encountered in response to injury
    • Thermal/chemical injury (e.g. smoking) to bronchial epithelium in the lung → squamous epithelium
    • Catheter creates inflammation in the bladder → transitional epithelium changes to squamous
  • Represents a change in signals to stem cells causing differentiation down a different line - not a reversal in appearance to adult cells
  • Metaplastic tissue is an at-risk site for the development of cancer