Overview
This lecture covers the classification, characteristics, spread, diagnosis, grading, and treatment of tumors, along with associated risk factors and common symptoms.
Tumor Nomenclature and Classification
- Tumors are named after their parenchyma (functional tissue of origin).
- Benign tumors end in "oma" (e.g., fibroma, chondroma).
- Malignant tumors of epithelial tissue are called carcinomas (e.g., squamous cell carcinoma, adenocarcinoma for glandular origin, melanoma for melanocytes).
- Malignant tumors of mesenchymal (connective) tissue are called sarcomas.
- Table 6-1 in the text provides more nomenclature examples.
Features of Benign and Malignant Tumors
- Benign tumors are well-differentiated, grow slowly, have a capsule, and do not invade or metastasize.
- Malignant tumors are poorly differentiated, grow rapidly, lack a capsule, invade tissues, and can metastasize.
- Cancer in situ refers to a malignant tumor that has not invaded beyond the basement membrane.
Invasion and Metastasis
- Metastasis occurs when tumor cells spread via blood or lymph to form secondary tumors.
- Sarcomas typically metastasize by blood; carcinomas by lymphatics.
- Carcinogenesis includes initiation (mutation), promotion (cell proliferation), and progression (additional mutations/competition).
- Angiogenesis (growth of new blood vessels) is essential for tumor survival and growth.
Causes and Risk Factors for Cancer
- Genetic predispositions (e.g., BRCA1, BRCA2, RB gene) raise cancer risk.
- Reproductive hormones, obesity, immune deficiency, and carcinogens (cigarettes, alcohol, diet, radiation, viruses, bacteria) contribute to cancer development.
- Viruses linked to cancer include HPV, Epstein-Barr virus, hepatitis B/C, and human T cell leukemia virus.
Symptoms and Systemic Effects of Cancer
- Cancer commonly causes weight loss and muscle wasting (anorexia-cachexia).
- Local effects include tissue compression and blood vessel erosion (e.g., blood in stool for colorectal cancer).
- Anemia, fatigue, sleep disturbances, and paraneoplastic syndromes (e.g., Cushing's syndrome from hormone secretion) may occur.
Diagnosis, Grading, and Staging
- Diagnosis methods include cytologic studies (e.g., Pap smear), tissue biopsies, and tumor marker assays.
- Tumor markers (e.g., PSA for prostate cancer) track diagnosis and treatment response.
- Microarray (gene chip) technology is used for classification and guiding therapy.
- Tumor grading (I-IV) is based on differentiation and mitotic figures; staging uses TNM (Tumor, Node, Metastasis) system.
Cancer Treatment Approaches
- Surgery removes tumors and surrounding tissue.
- Radiation therapy uses ionizing radiation to destroy tumor cells, often combined with surgery.
- Chemotherapy targets rapidly dividing cells systemically; explains hair loss.
- Hormone/anti-hormone therapy blocks hormone-driven cancer growth.
- Biotherapies/targeted therapies use monoclonal antibodies to mark cancer cells for immune destruction.
Childhood Cancers
- Childhood cancers are rare (1% of cases) with an 85% survival rate.
- Most are blood and bone marrow cancers (leukemias).
- Warning signs: prolonged fever, fatigue, bone pain, enlarged lymph nodes, weight loss, or growing mass.
Key Terms & Definitions
- Benign tumor — Non-cancerous growth, does not invade or metastasize.
- Malignant tumor — Cancerous growth, invades tissue, and can metastasize.
- Carcinoma — Malignant epithelial tumor.
- Sarcoma — Malignant tumor of connective tissue.
- Metastasis — Spread of cancer cells to distant sites.
- Angiogenesis — Formation of new blood vessels by tumors.
- TNM staging — Classification system: Tumor size, Node involvement, Metastasis.
Action Items / Next Steps
- Review Table 6-1 for tumor nomenclature examples.
- Learn the TNM staging classification for the exam.
- Note exam question expected on tumor naming.