Neoplasia — Classification, Grading, Staging & Tumor Biology
🟢 Lite — Quick Review (1h–1d)
Rapid summary for last-minute revision before your exam.
Benign vs Malignant:
- Benign: Well-differentiated, cohesive, encapsulated, no metastasis
- Malignant: Poorly differentiated, invasive, pleomorphism, hyperchromatic nuclei, mitotic figures, necrosis, metastasis
Tumor nomenclature:
- Epithelial: Benign = papilloma/adenoma; Malignant = carcinoma (squamous/adenocarcinoma)
- Mesenchymal: Benign = fibroma/leiomyoma; Malignant = sarcoma
- Mixed: Teratoma (contains all 3 germ layers)
Grading: Degree of differentiation (GX–G4); based on how much tumor resembles normal tissue. Staging: TNM — Tumor size (T), Nodes (N), Metastasis (M); most important prognostic factor.
Oncogenes: Gain of function;只需要one allele mutated (dominant); e.g., RAS, MYC, BCR-ABL (CML), HER2/neu. Tumor suppressor genes: Loss of function; requires BOTH alleles lost (recessive); e.g., RB (retinoblastoma), p53 (Li-Fraumeni), BRCA1/2, APC.
⚡ Exam tip: “2-hit hypothesis” = both alleles of tumor suppressor gene must be inactivated; explains why hereditary cancers occur earlier (1st hit is germline, 2nd is somatic).
🟡 Standard — Regular Study (2d–2mo)
Standard content for students with a few days to months.
Nomenclature
Benign Tumors
| Tissue | Benign Tumor | Example |
|---|---|---|
| Squamous epithelium | Squamous papilloma | Skin warts |
| Glandular epithelium | Adenoma | Colonic adenoma, thyroid adenoma |
| Fibroblasts | Fibroma | Soft tissue fibroma |
| Smooth muscle | Leiomyoma | Uterine leiomyoma (most common pelvic tumor in women) |
| Striated muscle | Rhabdomyoma | Cardiac rhabdomyoma (associated with tuberous sclerosis) |
| Blood vessels | Hemangioma | Strawberry hemangioma of infancy |
| Adipose | Lipoma | Most common soft tissue tumor |
| Nerve sheath | Schwannoma | Acoustic neuroma (vestibular schwannoma) |
Malignant Tumors
| Tissue | Malignant Tumor | Notes |
|---|---|---|
| Squamous epithelium | Squamous cell carcinoma | Keratin pearls, intercellular bridges |
| Glandular epithelium | Adenocarcinoma | Gland formation; mucin production |
| Basal cells | Basal cell carcinoma | Face; locally invasive; rare metastasis |
| Melanocytes | Melanoma | Most dangerous skin cancer; vertical growth phase |
| Fibroblasts | Fibrosarcoma | — |
| Smooth muscle | Leiomyosarcoma | Uterus, GI, retroperitoneum |
| Striated muscle | Rhabdomyosarcoma | Children; botryoid type in bladder/vagina |
| Bone | Osteosarcoma | Most common primary bone malignancy; peak 10–20 years |
| Cartilage | Chondrosarcoma | Adults; slow-growing |
| Fat | Liposarcoma | Retroperitoneum |
| Blood vessels | Angiosarcoma | Liver (vinyl chloride), spleen, breast |
| Nerve sheath | Malignant peripheral nerve sheath tumor (MPNST) | NF1-associated |
| Mesothelioma | — | Pleura; associated with asbestos exposure |
| Glioma | Astrocytoma, oligodendroglioma, glioblastoma | CNS |
| Lymphocytes | Lymphoma (Hodgkin and Non-Hodgkin) | — |
| Hematopoietic | Leukemia | — |
Special Tumor Terms
- Carcinoma in situ: Pre-invasive; cells haven’t breached basement membrane; e.g., carcinoma in situ of cervix (CIN), DCIS (ductal carcinoma in situ of breast)
- Leukemia: Malignant tumor of blood-forming cells; NO solid tumor
- Lymphoma: Solid tumor of lymphoid tissue; often presents with lymphadenopathy
- Sarcoma: Malignant tumor of mesenchymal origin
- Teratoma: Germ cell tumor containing tissues from all 3 germ layers; in ovary (mature cystic teratoma = dermoid cyst) or testis
- Choriocarcinoma: Gestational trophoblastic disease; very aggressive; produces β-hCG; sensitive to chemotherapy
- Dysgerminoma: Female germ cell tumor; analogous to seminoma in males; radiosensitive
- Yolk sac tumor (endodermal sinus tumor): Produces AFP; most common testicular germ cell