Oncopathology Explained CAT : Cancer OmpathStudy

EXAM PAPER DETAILS Mount Kenya University — School of Medicine Programme: Bachelor of Medicine and Bachelor of Surgery, Year 3 Assessment: End of Semester 1 — Continuous Assessment Test (CAT 2) Unit Code: MBPA 3412 — General Pathology II: Oncopathology Date: 8th December 2025 Time: 30 minutes SECTION A: Short Answer Questions (15 minutes) Q1: List the hallmarks of cancer. (5 marks) Q2: Give an outline of the classification of carcinogens. (10 marks) SECTION B: Long Answer Question (15 minutes) Q1: Describe the nomenclature of tumours. (15 marks) --- Now the full answers, matching the mark allocation: ONCOPATHOLOGY Question 1 — Hallmarks of Cancer (5 marks — need 5 clear points) 1. Self-sufficiency in growth signals — oncogene activation (RAS, MY C) → proliferates without external growth signals 2. Insensitivity to anti-growth signals — loss of tumour suppressors (p53, R B) → ignores stop signals 3. Evasion of apoptosis — p53 mutation, ↑BCL-2 → resists programmed cell death 4. Limitless replicative potential — telomerase reactivation → immortalization, avoids senescence 5. Sustained angiogenesis — VEGF secretion → new vessel formation for nutrient supply 6. Invasion and metastasis — ↓E-cadherin, matrix metalloproteinase secretion → basement membrane breach, spread (Extra, for a stronger answer beyond the classic 6): evasion of immune destruction, reprogrammed energy metabolism (Warburg effect), genome instability, tumour-promoting inflammation. --- Question 2 — Classification of Carcinogens (10 marks — needs categories + examples) 1. Chemical carcinogens Direct-acting: react with DNA directly, no activation needed (e.g. alkylating chemotherapy agents) Indirect-acting (procarcinogens, need metabolic activation): Polycyclic aromatic hydrocarbons (tobacco smoke, smoked food) → lung, skin cancer Aromatic amines/azo dyes → bladder cancer Nitrosamines (cured meats) → GI cancer Aflatoxin B1 ( Aspergillus , stored grains) → hepatocellular carcinoma Vinyl chloride → liver angiosarcoma Asbestos → mesothelioma, bronchogenic carcinoma 2. Physical carcinogens UV radiation → skin cancers (pyrimidine dimers) Ionizing radiation → leukaemia, thyroid, bone cancer Chronic irritation/foreign bodies 3. Biological carcinogens Viruses: HPV 16/18 (cervical Ca — E6/E7 degrade p53/RB), Hep B/C (HCC), EBV (Burkitt lymphoma, nasopharyngeal Ca), HTLV-1 (adult T-cell leukaemia), HHV-8 (Kaposi sarcoma) Bacteria: H. pylori → gastric adenocarcinoma, MALT lymphoma Parasites: Schistosoma haematobium → bladder SCC; liver flukes → cholangiocarcinoma 4. Hormonal carcinogens Unopposed oestrogen → endometrial carcinoma DES in utero → vaginal clear cell adenocarcinoma Mechanism (bonus line): initiation (irreversible mutation) → promotion (clonal expansion) → progression (further mutations → malignant phenotype). --- Section B: Nomenclature of Tumours (15 marks — needs structure + exceptions + examples) General rule: named by tissue of origin + suffix denoting benign or malignant behaviour. Benign tumours — suffix "-oma" Epithelial: adenoma (glandular), papilloma (surface projection), cystadenoma (cystic) Mesenchymal: lipoma (fat), fibroma (fibrous tissue), leiomyoma (smooth muscle), chondroma (cartilage), osteoma (bone), haemangioma (vessels) Malignant tumours Epithelial origin → carcinoma (squamous cell carcinoma, adenocarcinoma) Mesenchymal origin → sarcoma (liposarcoma, fibrosarcoma, leiomyosarcoma, osteosarcoma, chondrosarcoma, angiosarcoma) Mixed and special tumours Mixed tumour: 1 neoplastic cell line, single germ layer, e.g. pleomorphic adenoma of salivary gland Teratoma: from totipotent germ cells, tissue from all 3 germ layers (mature = benign, immature = malignant) Exceptions to the naming convention (important — examiners love these) Sound benign ("-oma") but are malignant : lymphoma, melanoma, mesothelioma, seminoma Hamartoma: benign, disorganized overgrowth of native tissue in its normal site Choristoma: benign, normal tissue in an abnormal location Leukaemia: malignant, named by "-aemia" not "-oma" Meningioma: benign, despite naming pattern Prefix guide (tissue of origin) Adeno- = gland, Lipo- = fat, Fibro- = fibrous tissue, Chondro- = cartilage, Osteo- = bone, Angio- = blood vessels, Rhabdomyo- = skeletal muscle, Leiomyo- = smooth muscle