Pathology of Dysplasia

Dysplasia

• Definition: Loss of uniformity of individual cells and loss of their architectural orientation
• May be a precursor to malignant transformation
• Characteristics:
  • Pleomorphism and large hyperchromatic nuclei with a high nuclear-to-cytoplasmic ratio
  • Mitotic figures are more abundant than in normal tissue and may be seen at all levels, including surface epithelial cells
• Can range from mild to severe (in-situ) and occur in various sites such as cervix, bladder, breast, and others
• Does not always progress to cancer

Carcinoma in Situ

• Definition: Marked dysplastic changes involving the full thickness of the epithelium, limited to the basement membrane
• Characteristics:
  • Atypical dysplastic cells replace the entire thickness of the epithelium
  • No orderly differentiation of squamous cells
  • Basement membrane is intact, and there is no tumor in the subepithelial stroma
• Early detection and screening programs increase detection of in situ carcinoma and increase survival rate

Cellular Interactions

• Cell-cell interactions
• Cell-stromal interactions with the basement membrane
• Interaction of tumor cells with the extracellular matrix (ECM) and mesenchymal stem cells (MSC)
• These interactions result in epithelial mesenchymal and stromal transition of tumor cells, their migration, invasion, and dissemination to distant organs

Differentiation

• Definition: Extent to which neoplastic tumor cells resemble the corresponding normal parenchymal cells, both morphologically and functionally
• Characteristics of a malignant cells/anaplasia:
  • Loss of differentiation
  • Pleomorphism nuclear and cellular
  • Increased nuclear cytoplasmic ratio
  • Hyperchromasia
  • Increased mitosis and abnormal mitosis
  • Loss of polarity

Classification of Tumors

• Based on biological behavior and morphologic characteristics
• Divided into:
  • Benign tumor
  • Malignant tumor

Components of Neoplasm

• Neoplastic cells: cells that form the tumor parenchyma
• Reactive stroma: the connective tissue, blood vessels, and cells of the immune system

Benign Tumor

• Definition: A tumor is benign when:
  • Tumors gross and microscopic appearances are innocent
  • Remain localized and will not spread to other sites
  • Local surgical removal is possible
• Patient generally survives
• Benign tumors are attached the suffix "-oma" to the name of the cell type from which the tumor originates (e.g. fibroma, chondroma, lipoma)

Malignant Tumors

• Referred collectively as cancer
• Characteristics:
  • Gross and microscopic appearances are aggressive
  • Invade and destroy adjacent structures
  • Spread to distant sites (metastasis)