Pathology

Pathology/B/01

General characteristics of neoplasms (benign, malignant tumors)

腫瘍（新生物）の一般的特徴（良性・悪性）

タグ
High-yield / ポイント

1. Definition

A neoplasm is an abnormal mass of tissue whose growth is uncontrolled, irreversible, and monoclonal (from one mother cell). It has two components:

  • Parenchyma — transformed neoplastic cells; determines biological behavior.
  • Stroma — non-neoplastic supporting tissue (connective tissue, vessels, inflammatory cells); essential for growth.

2. Hallmarks of cancer

  1. Autocrine growth — makes its own ligand + receptor.
  2. Insensitivity to growth inhibitors.
  3. Resistance to apoptosis.
  4. Limitless replication — never enters G0.
  5. Loss of differentiation.
  6. Angiogenesis (VEGF).
  7. Tissue invasion.
  8. Metastasis.
  9. Immune evasion.
  10. Metabolic reprogramming (aerobic → anaerobic, Warburg).

3. Nomenclature

  • Tumor = swelling; cancer = malignant tumor; carcinoma = malignant epithelial; sarcoma = malignant mesenchymal.
  • Benign tumors take the suffix “-oma” added to the cell of origin.

4. Benign vs malignant vs in-between

Benign Malignant Semi-malignant Borderline
Differentiation Yes No/variable Yes No/variable
Anaplasia No Yes/variable Variable Yes
Growth rate Slow Fast Slow Slow
Invasion Expansive Infiltrative Expansive Localized, BM preserved
Metastasis No Yes No No
  • Benign — expansive, pushes tissue aside, encapsulated, easily resected.
  • Malignant — invades and destroys, metastasizes (exception: brain tumors don’t metastasize outside CNS).
  • Semi-malignant — mixed behavior: basal cell carcinoma (malignant but rarely metastasizes) and pleomorphic adenoma of parotid (benign but recurs).
  • Borderline — atypical cytology without invasion; e.g. ovarian cystadenoma ↔ cystadenocarcinoma.

Anaplasia = lack of differentiation; the most reliable feature of malignancy.

💡 High-yield: Neoplasm = uncontrolled, monoclonal growth (parenchyma + stroma). Carcinoma = epithelial malignancy, sarcoma = mesenchymal; benign = “-oma”. Metastasis is the most reliable sign of malignancy. Semi-malignant: BCC, parotid pleomorphic adenoma. Borderline: ovarian tumors (BM preserved).