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Neoplasia and Tumor Classification Overview

Nov 24, 2024

Pathology Lecture Notes

Introduction

  • Speaker: Dr. Priyanka Sajdev
  • Audience: Second-year medical students
  • Focus: Crash course in pathology for university exams
  • Topics covered: Systemic pathology, hematology, general pathology
  • Current session focus: Neoplasia

Neoplasia Overview

  • Definition: Neoplasia means 'new growth'; it refers to the formation of abnormal tissue, known as neoplasm or tumor.
  • Types: Neoplasms can be benign or malignant.
  • Field of Study: Oncology is the branch that deals with neoplasms.

Normal vs. Neoplastic Cells

  • Normal cells: Cell division occurs only with a growth stimulus binding to a growth receptor.
  • Neoplastic cells: Uncontrolled cell division occurs even without growth stimuli.
    • Results in uncoordinated and excessive growth, forming a neoplasm.

Components of Neoplasia

  • Parenchyma: The tumor cells.
  • Stroma: The supporting tissue, consisting of blood vessels, fibrous tissue, etc.
    • Excessive fibrosis in stroma is known as desmoplasia.

Classification and Nomenclature

  • Benign Tumors: Have 'oma' suffix (e.g., adenoma, papilloma).
    • Exceptions: Melanoma, Seminoma, Hepatoma, Mesothelioma, Lymphoma (malignant despite 'oma').
  • Malignant Tumors:
    • Carcinomas: Arise from epithelial cells (squamous or columnar).
    • Sarcomas: Arise from mesenchymal cells (muscles, bones).

Special Tumors

  • Teratoma: Tumors from totipotent cells, containing elements from all three germ layers (ectoderm, mesoderm, endoderm).
  • Hamartoma: Abnormal tissue at a normal site.
  • Choreostoma: Normal tissue at an abnormal site.

Differentiating Benign and Malignant Tumors

Based on Growth

  • Benign: Slow growth.
  • Malignant: Rapid growth.

Based on Clinical Features

  • Benign: Usually asymptomatic.
  • Malignant: Often symptomatic.

Based on Gross Appearance

  • Benign: Well-circumscribed, encapsulated, compresses surrounding tissue.
  • Malignant: Irregular shape, non-capsulated, invades surrounding tissue.

Microscopic Features (Anaplasia)

  1. Loss of basal polarity.
  2. Presence of pleomorphism.
  3. Increased nucleus-cytoplasm (NC) ratio.
  4. Anisocytosis (variable cell size).
  5. Hyperchromatism (dark nucleus).
  6. Prominent nucleoli.
  7. Frequent mitoses.
  8. Presence of giant cells.
  9. Cytoplasmic mucin presence.
  10. Genetic abnormalities (aneuploidy).

Metastasis

  • Definition: Formation of secondary masses discontinuous from the primary tumor via blood or lymph.
  • Roots of Spread:
    1. Lymphatic: Carcinomas mostly.
    2. Hematogenous: Sarcomas mostly, via veins.
    3. Transcelomic: Via body cavities, e.g., Krukenberg's tumor (stomach to ovaries).

Steps of Hematogenous Metastasis

  1. Formation of aggressive tumor clone.
  2. Loss of cell adhesion (via E-cadherin).
  3. Interaction with ECM (extracellular matrix).
  4. Degradation of ECM.
  5. Intravasation into blood vessels.
  6. Formation of thrombus to evade immune system.
  7. Extravasation to distant sites.
  8. Formation of secondary tumor mass.

Note: Benign tumors do not metastasize; malignant ones generally do, with exceptions like glioma and basal cell carcinoma.

Conclusion

  • Important additional topics include carcinogenesis, paraneoplastic syndromes, and tumor markers.
  • Upcoming sessions will cover hemodynamics, including edema, thrombosis, embolism, and shock.

Full transcript