Defining Neoplasia

Defining Neoplasia

• Neoplasia refers to new growth, and is a disorder of cell growth triggered by genomic alterations.
• Neoplasia is characterized by excessive proliferation of cells, which is uncontrolled by physiological growth signals.
• Neoplastic cells gain a survival and growth advantage over normal cells.
• Neoplastic cells are clonal, meaning they arise from a single progenitor cell.
• Distinguishing Neoplasia from Normal Growth: Neoplasia is distinguished from other forms of new growth, such as wound repair, hyperplasia, and hypertrophy, by its unregulated, irreversible, and clonal nature.
• Hyperplasia: Increase in the number of cells in response to a stimulus, which can be physiological or pathological. Hyperplasia ends when the stimulus is removed. Examples include thickening of the endometrium during the menstrual cycle.
• Hypertrophy: Increase in the size of cells, without an increase in cell number. It involves increased protein production within the cells and can be physiological or pathological. Muscle hypertrophy is a good example.
• Metaplasia: Reversible change where one differentiated cell type is replaced by another, usually in response to tissue damage, repair, or regeneration. The new cell type is typically better suited to the altered environment. Stem cells are reprogrammed to differentiate along a new pathway.

Neoplasm Types: Benign vs. Malignant

• Benign Neoplasms: Stay localized, do not spread (metastasize), are well-circumscribed, and non-infiltrative. They are often resectable by surgery.
• Malignant Neoplasms (Cancer): Exhibit invasive growth, destroying surrounding tissues. Can spread to distant sites (metastasize), with approximately 30% of tumors initially presenting as metastatic disease. Treatment is complex, particularly in advanced stages, and prognosis can be uncertain.

Neoplasm Nomenclature

• The beginning of the name identifies the tissue of origin, such as:
  • Myo-: muscle (leiomyo- smooth muscle, rhabdomyo- skeletal muscle)
  • Neuro/schwanno-: neural tissue
  • Lipo-: adipose tissue (fat)
  • Fibro-: fibrous connective tissue
  • Angio-: vessel (hemangio - blood vessel, lymphangio - lymph vessel)
• The ending of the name indicates the tumor type
  • -oma: Typically means tumor and is usually benign.
  • -carcinoma: Epithelial malignancy
    • Adenocarcinoma: Glandular features
  • -sarcoma: Mesenchymal malignancy
• Exceptions: Some terms don't follow the standard naming conventions (e.g., Lymphoma, Leukemia, Melanoma, Mesothelioma).

Dysplasia

• Intraepithelial Neoplasia: Genetically altered cells remain within the epithelium. The basement membrane acts as a barrier, preventing aggressive growth and metastasis.
• Dysplasia as a Precursor to Carcinoma: When dysplasia invades through the basement membrane into the connective tissue, it transforms into carcinoma.
• Carcinoma in situ: Dysplasia involving the full thickness of the epithelium but still confined by the basement membrane. Surgical excision is often curative.

Teratomas and Hamartomas

• Teratoma: Benign tumor containing cells and tissues from multiple tissue types and germ layers (endoderm, mesoderm, ectoderm). Originates from germ cells, which are totipotent stem cells found in the testes and ovaries.
• Hamartoma: Benign proliferation of cells and tissues native to the involved site. Considered a highly differentiated benign neoplasm.
• Choristoma: Benign proliferation of cells and tissues found in a non-native location. Also considered a highly differentiated benign neoplasm.

Key Facts about Cancer Epidemiology

• Cancer is the second leading cause of death in both adults and children worldwide, after cardiovascular disease.
• The most common cancers by incidence in adults are: Breast/prostate, Lung, Colorectal.
• The most common causes of cancer mortality in adults are: Lung, Breast/prostate, Colorectal cancer.
• The lifetime risk of developing cancer is 40% for males and 39% for females, with a risk of death of 21% for men and 18% for women.
• The ‘big 4’ cancers (lung, breast, prostate, colorectal) account for approximately 50% of US cancer diagnoses and deaths.
• Overall cancer death rates have decreased in the last 20-25 years due to changes in risk factors, increased cancer screening, and better therapy.
• Screening programs aim to detect dysplasia (precancerous change) before it progresses into carcinoma, or to identify carcinoma early before symptoms arise. The goal is to reduce cancer-specific mortality.

Acquired Predisposing Conditions

• Immunodeficiency: Intact T-cell immunity is critical for normal cell surveillance, and deficiencies in immune function increase cancer risk (e.g., HIV/AIDS, chronic immunosuppression).
• Precursor Lesions:
  • Metaplasia: A reversible change in cell type, often associated with tissue damage, repair, or regeneration (e.g., Barrett’s esophagus).
  • Hyperplasia: An increase in the number of cells in response to a stimulus. It can be a precursor to cancer (e.g., endometrial hyperplasia).
  • Dysplasia: Altered cell growth that can, over time, lead to cancer.
  • Benign Neoplasia: Although benign, some can have precancerous potential (e.g., colorectal adenoma).

Genetics and Cancer

• Genetics plays a crucial role in cancer development.
• Certain genetic predispositions can increase an individual's risk of developing specific types of cancer.
• An example of a genetic syndrome associated with increased cancer risk is nevoid basal cell carcinoma syndrome (NBCCS).

This quiz explores the concept of neoplasia, focusing on its characteristics, mechanisms of cell growth, and how it differs from normal physiological processes. You will learn about the implications of clonal proliferation and the distinction between neoplasia, hyperplasia, and hypertrophy.