Kuliah 9

• Neoplasia


  A tissue growth that is unregulated, irreversible, and monoclonal
• Neoplasia


  • Unregulated; does not follow the normal mechanism
  • Irreversible; can not be changed back
  • Monoclonal; derived from a single mother cell
• Neoplasia is distinguished from hyperplasia and repair
• Benign tumors


  Remain localized at their site of origin and are generally controlled by surgical removal
• Malignant tumors


  Can invade and destroy adjacent structures and spread to distant sites (metastasize)
• Tumor nomenclature is based on

  • Lineage of differentiation (type of tissue produced)
  • The behavior of tumor cells (benign or malignant)
• Benign tumor nomenclature


  • Cell of origin (e.g. adenoma, fibroma)
  • Microscopic appearance (e.g. cystadenoma)
  • Macroscopic architecture (e.g. papilloma)
• Malignant tumors


  Generally called "cancers" (latin word for crab)
• Malignant tumor classification based on cell of origin

  • Epithelial cells: carcinomas
  • Mesenchymal cells: sarcomas (Greek sar = fleshy)
  • Blood-forming cells: leukemias (literally, white blood)
  • Immune cells and precursors: lymphomas
• Types of cells in our body

  • Epithelial
  • Mesenchymal
  • Hematolymphoid
  • Neuroendocrine
  • Germ cell
• Tumor nomenclature examples


  • Epithelial: Adenocarcinoma, Papillary carcinoma
  • Mesenchymal: Liposarcoma, Chondrosarcoma, Osteogenic sarcoma
  • Hematolymphoid: Lymphoma/Leukemia
  • Melanocyte: Melanoma
  • Germ cell: Embryonal carcinoma, Choriocarcinoma, Seminoma
• Hamartomas are disorganized masses composed of cells indigenous to the involved tissue, with clonal chromosomal aberrations, and are considered benign neoplasms
• Choristomas are heterotopic (misplaced) rests of cells, such as ectopic pancreas
• Summarized comparison between benign and malignant tumors

  • Differentiation/anaplasia
  • Rate of growth
  • Local invasion
  • Metastasis
• Differentiation


  The resemblance of neoplastic parenchymal cells to the corresponding normal parenchymal cells, both morphologically and functionally
• Anaplasia


  Lack of differentiation
• Benign tumors are generally well differentiated, with rare and normal mitotic figures
• Malignant tumors show varying degrees of differentiation, from well to poorly differentiated, with numerous and abnormal mitotic figures
• Benign tumors


  • Cohesive, expansile, well-demarcated masses that do not invade or infiltrate surrounding normal tissues
  • Easily excisable by surgery (except hemangioma)
• Malignant tumors


  • Locally invasive, infiltrating surrounding tissue
  • Difficult surgical resection
• Other characteristics of malignant tumors

  • Pleomorphism (variation in cell size and shape)
  • Abnormal nuclear morphology
  • Nuclei disproportionately large to cytoplasm
  • Hyperchromatic, irregular, abnormally large nucleoli
  • High rate of atypical, bizarre mitotic figures
  • Loss of polarity and disturbed basement membranes
  • Ischemic necrosis due to insufficient blood supply
• Lesion


  • Retracted and infiltrates the surrounding breast substance
  • Stony hard on palpation
• Low-power microscopic view


  • Irregular infiltrative borders without a well-defined capsule
  • Intense stromal reaction
• Pleomorphism


  Variation in cell size and shape
• Abnormal nuclear morphology


  • Nuclei that are disproportionately large to ratio 1:1 (normal 1:4 to 1:6)
  • Often irregular
  • Hyperchromatic
  • Abnormally large nucleoli
• Mitoses


  • High rate of proliferation
  • Feature of malignancy
  • Atypical, bizarre mitotic figures
• Loss of polarity


  • Basement membranes disturbed, disorganized fashion
• Ischemic necrosis


  • Insufficient blood supply to the tumor cells
• Pleomorphic tumor of the skeletal muscle

  • Rhabdomyosarcoma
• Note the marked cellular and nuclear pleomorphism, hyperchromatic nuclei, and tumor giant cells
• Comparison between Benign and Malignant Tumors

  • Benign (Leiomyoma): Tumor small, well demarcated, slow growing, noninvasive, well differentiated, nonmetastatic
  • Malignant (Leiomyosarcoma): Rapidly growing with hemorrhage and necrosis, locally invasive, metastatic, poorly differentiated, large, poorly demarcated
• Metaplasia


  Replacement of one type of mature cell with another type of mature cells, found in association with tissue damage, repair, and regeneration = adaptation to chronic injury
• Examples of metaplasia


  • Intestinal metaplasia in Barrett's esophagus, squamous metaplasia in cervicitis
• Dysplasia


  Premalignant change, lost polarity and maturity of cells
• Examples of dysplasia


  • Dysplasia in adenoma, intra-epithelial dysplasia in cervix
• Carcinoma in situ


  A cancer that has yet to invade
• Damage to DNA of stem cells leads to cancer, as the damage overcomes DNA repair mechanisms but is not lethal
• Carcinogens damage DNA, increasing the risk for cancer
• DNA mutations disrupt key regulatory systems, leading to increased growth and spread
• Proto-oncogenes


  Normal cellular genes whose products promote cell proliferation, 'the gas'