🟢 Lite — Quick Review (1h–1d)
Neoplasia = uncontrolled cell proliferation independent of normal growth stimuli. Tumors arise from mutated cells that escape apoptosis and grow autonomously. Benign tumors are encapsulated, well-differentiated, and don’t metastasize (e.g., lipoma, adenoma). Malignant tumors are poorly differentiated, invade surrounding tissues, and spread via lymphatic/hematogenous routes (e.g., carcinoma, sarcoma). Key nomenclature: epithelial tumors ending in “-oma” are usually benign (adenoma), while malignant epithelial tumors are “-carcinoma” and malignant mesenchymal tumors are “-sarcoma.” Tumor suppressor genes (Rb, p53) inhibit growth; oncogenes (RAS, MYC) promote growth. Cancers spread by direct extension, lymphatic invasion, hematogenous spread, or seeding. Grading = microscopic differentiation; Staging = extent of spread (TNM: Tumor size, Node involvement, Metastasis). Tumor markers include AFP (liver cancer), CEA (colon cancer), CA-125 (ovarian cancer), PSA (prostate cancer), and hCG (choriocarcinoma).
🟡 Standard — Regular Study (2d–2mo)
Definitions
A neoplasm (tumor) is an abnormal mass of tissue whose growth exceeds and is uncoordinated with that of normal tissues, persisting even after the stimulus is removed. Cancer is the lay term for malignant neoplasms. Unlike hyperplasia (controlled, excessive cell division), neoplasia is autonomous — it continues without external growth signals.
Benign vs Malignant Tumors
| Feature | Benign | Malignant |
|---|---|---|
| Differentiation | Well-differentiated | Poorly differentiated / anaplastic |
| Growth rate | Slow | Rapid |
| Border/Encapsulation | Encapsulated, pushing borders | Infiltrative, irregular borders |
| Metastasis | Absent | Present |
| Necrosis | Rare | Common |
| Mitotic figures | Few | Numerous, abnormal |
| Nuclear features | Uniform nuclei | Pleomorphism, hyperchromasia, prominent nucleoli |
Key Terminology
- Differentiation: Degree to which tumor cells resemble normal tissue
- Anaplasia: Loss of differentiation, primitive cells with large hyperchromatic nuclei, giant cells, and atypical mitoses
- Dysplasia: Abnormal cell growth with loss of uniformity and architectural orientation; may progress to carcinoma in situ
- Carcinoma in situ (CIS): Pre-invasive malignancy confined to epithelium with basement membrane intact; not yet metastatic
Tumor Nomenclature
- Adenoma: Benign glandular tumor (e.g., colorectal adenoma)
- Carcinoma: Malignant tumor of epithelial origin
- Sarcoma: Malignant tumor of mesenchymal origin (e.g., osteosarcoma, leiomyosarcoma)
- Papilloma: Benign exophytic growth on mucosal surfaces
- Papillary carcinoma: Carcinoma with papillary architecture (e.g., papillary thyroid carcinoma)
- Cystadenoma/Cystadenocarcinoma: Tumors with cystic architecture
Oncogenesis — Two-Gene Model
-
Proto-oncogenes → Oncogenes: Normal growth-promoting genes that become cancer-causing via mutation or amplification
- Examples: RAS (GTPase, signal transduction), MYC (transcription factor), HER2/NEU (growth factor receptor), BCL-2 (anti-apoptotic), cyclin D1 (cell cycle)
-
Tumor Suppressor Genes: Normally inhibit cell proliferation; loss leads to uncontrolled growth
- Rb (Retinoblastoma): Inhibits G1→S cell cycle transition; both alleles must be lost
- p53 (“Guardian of Genome”): Induces apoptosis in damaged cells; mutated in ~50% of all human cancers
- BRCA1/BRCA2: DNA repair; mutations → breast/ovarian cancer
- APC: Tumor suppressor in colon; loss → familial adenomatous polyposis (FAP)
TNM Staging
- T: Size and local extent of primary tumor
- N: Regional lymph node involvement
- M: Distant metastasis
Stage grouping: Stage I (localized, small) → Stage IV (distant metastasis)
Common Tumor Markers
| Marker | Associated Tumor |
|---|---|
| AFP | Hepatocellular carcinoma, yolk sac tumor |
| CEA | Colorectal carcinoma, pancreatic cancer |
| CA-125 | Ovarian serous carcinoma |
| CA19-9 | Pancreatic adenocarcinoma |
| PSA | Prostate adenocarcinoma |
| hCG | Choriocarcinoma, embryonal carcinoma |
| CA15-3 | Breast adenocarcinoma |
| S-100 | Melanoma, schwannoma |
| Chromogranin | Neuroendocrine tumors |
| Calcitonin | Medullary thyroid carcinoma |
🔴 Extended — Deep Study (3mo+)
Epidemiology and Risk Factors
Cancer is the second leading cause of death globally. In India, the most common cancers in males are lung, mouth, esophagus, and stomach; in females, breast, cervix, and ovarian cancer rank highest. Major risk factors include tobacco (squamous cell carcinoma of lung, oral cavity), HPV infection (cervical cancer, oropharyngeal SCC), HBV/HCV (hepatocellular carcinoma), Helicobacter pylori (gastric cancer), dietary factors (processed meat → colorectal cancer), alcohol (hepatocellular carcinoma, esophageal SCC), obesity (endometrial, breast, colon cancer), and ionizing radiation (leukemia, solid tumors).
Hallmarks of Cancer (Hanahan & Weinberg)
- Self-sufficiency in growth signals — autonomous signaling
- Insensitivity to growth-inhibitory signals — bypass of tumor suppressors
- Evasion of apoptosis — resistance to programmed cell death (e.g., BCL-2 overexpression)
- Replicative immortality — telomerase activation
- Sustained angiogenesis — VEGF-driven new vessel formation
- Invasion and metastasis — EMT (epithelial-mesenchymal transition), loss of E-cadherin
- Dysregulated metabolism — Warburg effect (aerobic glycolysis)
- Immune evasion — PD-L1 expression, Treg infiltration
- Genome instability — mutations in DNA repair genes
- Tumor-promoting inflammation — inflammatory cytokines support growth
Carcinogens
- Chemical carcinogens: Direct-acting (alkylating agents) and indirect-acting (polycyclic aromatic hydrocarbons — benzo[a]pyrene in tobacco smoke; aflatoxin B1 → liver cancer; asbestos → mesothelioma; nitrosamines)
- Radiation: Ionizing radiation (X-rays, gamma rays, radon) causes DNA double-strand breaks; UV radiation → pyrimidine dimers → melanoma, SCC
- Viral oncogens:
- HPV (types 16, 18) → E6 (inactivates p53) and E7 (inactivates Rb) → cervical, oropharyngeal SCC
- HBV/HCV → chronic inflammation → hepatocellular carcinoma
- EBV → Burkitt lymphoma, nasopharyngeal carcinoma, post-transplant lymphoproliferative disorder
- HTLV-1 → Adult T-cell leukemia/lymphoma (Tax protein)
- HIV → indirectly via immunosuppression → Kaposi sarcoma (HHV-8), NHL
Paraneoplastic Syndromes
Remote effects of cancer not due to direct invasion or metastasis:
- Hypercalcemia: PTHrP secretion (squamous cell lung cancer, breast cancer), osteolytic bone metastases
- Cushing syndrome: ACTH secretion (small cell lung cancer)
- SIADH: ADH secretion (small cell lung cancer)
- Erythrocytosis: EPO secretion (renal cell carcinoma, hepatocellular carcinoma)
- Thrombophlebitis (Trousseau syndrome): Mucin-secreting adenocarcinomas (gastric, pancreatic)
- Lambert-Eaton myasthenic syndrome: Anti-VGCC antibodies (small cell lung cancer)
- Acanthosis nigricans: Associated with gastric adenocarcinoma
- Hypertrophic osteoarthropathy: Clubbing, periostitis (lung cancer)
Tumor Spread
| Mode | Route | Example |
|---|---|---|
| Direct extension | Invades adjacent tissues | Cervical cancer → bladder/rectum |
| Lymphatic spread | Lymphatics → regional nodes | Carcinoma → regional LN; Sarcoma → hematogenous |
| Hematogenous spread | Veins (portal → liver, caval → lung) | RCC → lung via IVC; osteosarcoma → lung |
| Seeding | Body cavities/surfaces | Ovarian carcinoma → peritoneum (peritoneal carcinomatosis) |
| Perineural spread | Along nerves | Pancreatic adenocarcinoma |
Note: Epithelial tumors (carcinomas) typically spread via lymphatics first; mesenchymal tumors (sarcomas) typically spread via blood first.
Grading vs Staging
-
Grading: Histologic/microscopic assessment — how abnormal do tumor cells look?
- Grade I: Well-differentiated
- Grade II: Moderately differentiated
- Grade III: Poorly differentiated
- Grade IV: Anaplastic/undifferentiated
-
Staging: Clinical/surgical extent of disease (TNM)
- Stage 0: Carcinoma in situ
- Stage I: Small, localized
- Stage II: Larger but still localized
- Stage III: Regional spread
- Stage IV: Distant metastasis
Common Organ System Tumors (High-Yield)
| Organ | Benign | Malignant (Common Type) |
|---|---|---|
| Esophagus | — | Squamous cell carcinoma (upper 2/3), Adenocarcinoma (lower 1/3, Barrett’s) |
| Stomach | — | Adenocarcinoma (intestinal type, H. pylori associated) |
| Colon | Adenomatous polyp | Adenocarcinoma (sequence: normal → adenoma → carcinoma, APC mutation) |
| Lung | — | Adenocarcinoma (most common overall), Squamous cell carcinoma (central, smoking), Small cell carcinoma (central, neuroendocrine) |
| Breast | Fibroadenoma, Phyllodes tumor | Infiltrating ductal carcinoma (most common), Infiltrating lobular carcinoma |
| Prostate | BPH (not a tumor) | Adenocarcinoma (Gleason scoring important) |
| Cervix | — | Squamous cell carcinoma (HPV 16/18), Adenocarcinoma |
| Liver | Hepatic adenoma | Hepatocellular carcinoma (HBV/HCV, cirrhosis), Cholangiocarcinoma |
| Thyroid | Thyroid adenoma | Papillary thyroid carcinoma (most common, good prognosis), Follicular, Medullary, Anaplastic |
| Brain | Meningioma, Schwannoma | Glioblastoma multiforme (Grade IV astrocytoma) |
INI CET Question Patterns and High-Yield Associations
- “Gardner syndrome” = APC mutation → colonic polyps + osteomas + desmoid tumors
- “Li-Fraumeni syndrome” = p53 mutation → breast cancer, sarcomas, brain tumors
- “Bloom syndrome” = DNA helicase defect → pancytopenia, AML
- “Xeroderma pigmentosum” = defective nucleotide excision repair → skin cancers
- “Burkitt lymphoma” = t(8;14) — MYC translocation; associated with EBV, endemic in Africa (jaw), sporadic (abdominal)
- “Follicular lymphoma” = t(14;18) — BCL-2 translocation (anti-apoptotic)
- “CML” = t(9;22) Philadelphia chromosome — BCR-ABL fusion
- “Papillary thyroid carcinoma” = RET/PTC rearrangements, BRAF V600E mutation; good prognosis; “Orphan Annie eye” nuclei with grooves
- “Medullary thyroid carcinoma” = calcitonin secretion; associated with MEN 2A/2B
- “Barrett esophagus” = intestinal metaplasia of esophagus → adenocarcinoma
- “Peutz-Jeghers syndrome” = STK11 mutation → GI hamartomatous polyps + mucocutaneous pigmentation
- “Hereditary nonpolyposis colorectal cancer (HNPCC/Lynch syndrome)” = DNA mismatch repair gene mutations (MLH1, MSH2) → microsatellite instability
- “BRCA1/BRCA2” mutations → breast and ovarian cancer; BRCA1 also triple-negative breast cancer
- “Philadelphia chromosome” = t(9;22) BCR-ABL → CML and some ALL
⚡ Exam Tips for INI CET (AIIMS PG):
- For staging questions: always identify T (size/invasion), N (nodes), M (metastasis) before answering
- Tumor markers: AFP = liver cancer + yolk sac tumor; CEA = colorectal; PSA = prostate; CA-125 = ovarian; hCG = choriocarcinoma
- Remember: carcinoma = epithelial, sarcoma = mesenchymal, lymphoma = lymphoid, leukemia = blood
- Proto-oncogenes are dominant (one copy mutation is enough); tumor suppressor genes are recessive (two-hit hypothesis by Knudson)
- p53 is the most commonly mutated gene in human cancer (~50%)
- Most common cancer in Indian males = lung; females = breast
- HPV E6 inactivates p53; HPV E7 inactivates Rb — classic INI CET concept
- Warburg effect = cancer cells rely on aerobic glycolysis even with oxygen (glycolysis + lactate production)
- Angiogenesis is necessary for tumor growth beyond 1-2mm³ — VEGF is key