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Basis of spontaneous regression of tumour Robbins based md pathology exam easy explanation

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Robbins pathology spontaneous regression tumour immune mechanisms

Basis of spontaneous regression of tumour

Spontaneous regression means partial or complete disappearance of a tumour without adequate treatment.
In Robbins, this phenomenon is one of the observations supporting immune surveillance against cancer.

Simple explanation

  1. Tumour cells develop new abnormal antigens
    • Because of mutations, cancer cells may express proteins that are not present, or are very low, in normal cells.
    • These are called tumour antigens.
  2. The immune system recognizes these cells as abnormal
    • Mainly CD8+ cytotoxic T lymphocytes attack and kill tumour cells.
    • NK cells also kill tumour cells, especially when the tumour has reduced MHC class I expression.
    • Macrophages and cytokines such as interferon-gamma can assist.
  3. If immune response becomes strong enough, the tumour may shrink or disappear
    • This is called spontaneous regression.
    • It is uncommon, but it provides evidence that the immune system can control tumour growth.

Tumours where it is classically described

  • Malignant melanoma
  • Renal cell carcinoma
  • Neuroblastoma, especially in infants
  • Some lymphomas/leukemias
  • Occasionally choriocarcinoma

One-line MD pathology answer

Spontaneous regression of some tumours supports the concept of immune surveillance, in which tumour-specific antigens are recognized and destroyed chiefly by cytotoxic T cells and NK cells.

Important exam point

It does not mean immunity always prevents cancer. Tumours can evade immunity by:
  • Losing tumour antigens
  • Decreasing MHC class I expression
  • Producing immunosuppressive factors such as TGF-beta
  • Expressing checkpoint ligands such as PD-L1
So, the final idea is:
Cancer may regress when host antitumour immunity overcomes tumour immune-evasion mechanisms.
The medical literature describes immune activation and tumour-cell apoptosis as leading proposed mechanisms, but spontaneous regression remains rare and is not fully explained in every case. A recent systematic review of reported head and neck SCC regressions illustrates that it is a recognized but exceptional event (PubMed PMID 39582210).
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