Q.(a) Differentiate between malignant and benign tumours.
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Start your 14-day free trial to unlock the full solution →The key difference is that benign tumours stay localised and do not spread, while malignant tumours invade nearby tissues and metastasise to distant sites. The most feared property of a malignant tumour is metastasis — the ability to break away, travel through blood or lymph, and form secondary tumours elsewhere in the body.
The Concept: What Makes a Tumour "Bad"?
A tumour is simply an abnormal mass of cells caused by uncontrolled division. But not all tumours are equally dangerous. The critical distinction lies in behaviour — does the tumour respect its boundaries, or does it invade and spread?
Think of a benign tumour like a well-behaved houseplant in a pot. It grows, sometimes quite large, but it stays inside its container. A malignant tumour, by contrast, is like an invasive weed — its roots push through the pot, spread into the garden, and send seeds to other parts of the yard. That ability to "send seeds" is what makes it truly dangerous.
(a) Differentiating Benign and Malignant Tumours
Let's compare them across the features that matter most in medicine:
| Feature | Benign Tumour | Malignant Tumour |
|---|---|---|
| Growth rate | Slow, often stops or grows very gradually | Rapid, continuous growth |
| Border | Well-defined, encapsulated (smooth edges) | Irregular, poorly defined — invades surrounding tissue |
| Spread | Remains localised; does not invade nearby tissues or metastasise | Invades adjacent tissues and can metastasise via blood or lymph |
| Cell appearance | Cells resemble normal tissue (well-differentiated) | Cells look abnormal (poorly differentiated or anaplastic) |
| Recurrence after removal | Rare — usually does not come back if fully removed | Common — may recur even after surgery |
| Effect on host | Usually not life-threatening unless it compresses a vital organ (e.g., brain) | Life-threatening — destroys tissue, causes cachexia, and spreads |
A common mistake is to think "benign = harmless." A benign brain tumour can be fatal if it grows inside the skull and compresses critical structures. The key is spread, not just location.
(b) The Most Feared Property: Metastasis
The single most dangerous characteristic of a malignant tumour is metastasis.
What is metastasis?
Metastasis is the process by which cancer cells break away from the primary tumour, travel through the bloodstream or lymphatic system, and establish secondary tumours in distant organs. This is what makes cancer a systemic disease rather than a local problem.
Why is it so feared?
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It makes the cancer incurable by local treatment alone.
Surgery or radiation can remove a primary tumour, but if cells have already seeded the liver, lungs, or brain, those treatments cannot reach every microscopic deposit.
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It causes organ failure.
Metastatic tumours disrupt the function of vital organs. For example, lung metastases impair breathing, liver metastases cause jaundice and metabolic failure, and brain metastases lead to neurological deficits.
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It is the cause of most cancer deaths. …
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