5.2

• Neoplasia


  New (neo) growth (plasia)
• Neoplasm


  • Abnormal (aberrant differentiation) mass of cells with excessive autonomous growth uncoordinated with surrounding normal tissue
  • All the features of dysplasia PLUS the acquisition of autonomous (immortal) proliferation of cells
  • Neoplasia is an irreversible change
• Immortality


  1. Normal cells can only replicate a limited number of times (50-70 times)

  2. Neoplastic cells express the ribonucleoprotein telomerase

  3. Telomerase adds new DNA onto the ends of the chromosome

  4. This maintains stable telomere ends to the chromosome

  5. This allows the cell to replicate indefinitely
• Normal cells become senescent


  Chromosome ends shorten with each cycle
• Neoplastic cells "switch on" the gene that leads to expression of the telomerase enzyme


  Can always form a telomere regardless of the number of cell divisions
• Growth (excessive proliferation)


  1. Neoplastic cells - replication is without limit

  2. Neoplastic cells have overcome the normal cell cycle checkpoints
• The change from a normal to a neoplastic cell is due to a mutational event in the cell genome (somatic mutation)
• Mutation is the result of spontaneous errors during cell division or DNA damaging agents
• These changes in the cell genome lead to activation of oncogenes and loss of tumour suppressor genes
• Most neoplasms arise from the clonal expansion of a single cell that has undergone neoplastic transformation
• Neoplastic change is NOT reversible, unlike metaplasia
• Neoplasia


  • Abnormal (inappropriate) differentiation
  • Aberrant lack of control (dysfunctional cellular communication & atypical tissue architecture)
  • Autonomous & immortal cell growth (proliferation)
• Abnormal Proliferation


  Cells escape from normal control and have enhanced replication ability
• Abnormal Differentiation


  Impaired (inappropriate) differentiation is observed
• Abnormal Relationship with stroma

  • Altered relationship between the neoplastic cells and the normal supportive tissue surrounding them
  • Lack of appropriate cell-to-cell communication
  • Recruit the surrounding tissue to provide nutrients/O2
  • Angiogenesis
  • Invade the surrounding tissue
  • Epithelial-mesenchymal transition
• Neoplasms can be sub-classified as either benign or malignant
• Benign neoplasia


  • Grow as a compact mass (within) the tissue as they expand
  • Distort but don't destroy and invade
• Malignant neoplasia


  • Cells invade and destroy the surrounding tissue as they grow and may spread to distant sites
• Benign neoplasia


  • Confined to site of origin
  • Benign epithelial neoplasms often form "polyps"
  • Expansive growth
  • Histologically closely resemble the parent cell
  • Growth rate is relatively slow
  • Abnormal relationship to surrounding tissue
• Benign neoplasia


  • Polyps
• Benign neoplasia do not metastasise
• Benign neoplasia are rarely lethal
• Malignant neoplasia


  • Poorly circumscribed
  • Strands of neoplastic tissue extend into the normal tissue
  • Produce enzymes that degrade extracellular matrix = invasion
  • Often have central necrosis
  • Surfaces are often ulcerated
  • Histologically less resemblance to parent cell
• Malignant neoplasia are not encapsulated, invasive, have a high growth rate, metastasise, and are often lethal
• Classification of neoplasms


  • Biological behaviour (benign vs malignant)
  • Tissue of origin (histogenesis)
  • Organ of origin
• Histogenesis nomenclature


  • Benign neoplasia - "tumours" = oma
  • Malignant neoplasia - "cancers"
  • Carcinoma (epithelial tissue)
  • Sarcoma (connective/supportive tissues)
• Benign epithelial neoplasia


  • Papilloma
  • Adenoma
• Malignant epithelial neoplasia


  • Squamous cell carcinoma
  • Adenocarcinoma
• Connective/supportive tissue neoplasia


  • Fibrous (fibroma, fibrosarcoma)
  • Nerve sheath (neurofibroma, neurofibrosarcoma)
  • Adipose (lipoma, liposarcoma)
  • Smooth muscle (leiomyoma, leiomyosarcoma)
  • Striated muscle (rhabdomyoma, rhabdomyosarcoma)
  • Cartilage (chondroma, chondrosarcoma)
  • Bone (osteoma, osteosarcoma)
• Lymphoid and haematopoietic neoplasia

  • Myeloproliferative or myelodysplastic disorders (benign)
  • Leukaemia
  • Malignant lymphoma
  • Hodgkin's disease (lymphoma)
  • Multiple myeloma
• Leukaemia literally means "white blood"
• Myelogenous and lymphocytic leukaemias

  • Common myeloid progenitor
  • Common lymphoid progenitor
• Tissue of origin (Histogenesis)


  • Benign
  • Malignant
• Benign neoplasms of the haemopoietic system

  • Myeloproliferative disorders
• Leukaemia


  Literally means "white blood"
• Lymphoid and haematopoietic neoplasia

  • Myelogenous leukaemia's
  • Lymphocytic leukaemia's
• Multipotential hematopoietic stem cell (Hemocytoblast)


  • Gives rise to common myeloid progenitor and common lymphoid progenitor
• Cells derived from multipotential hematopoietic stem cell

  • Erythrocyte
  • Mast cell
  • Myeloblast
  • Natural killer cell
  • T lymphocyte
  • B lymphocyte
  • Megakaryocyte
  • Basophil
  • Neutrophil
  • Eosinophil
  • Monocyte
  • Plasma cell
  • Macrophage
• Leukaemia accounts for ~30% of lymphoid and haematopoietic neoplasia
• Lymphoma accounts for ~55% of lymphoid and haematopoietic neoplasia