Question

Define cancer.

Answer 1

Step 1: Definition:
Cancer is a disease in which some of the body's cells lose the normal control over cell division and grow in an uncontrolled, abnormal manner, invading and damaging the surrounding normal tissue.

Step 2: Key Feature: Metastasis:
Unlike a benign tumour, malignant (cancerous) cells can undergo metastasis — they break away, enter blood or lymph vessels, and travel to distant parts of the body to form new (secondary) tumours.

Step 3: Underlying Cause:
This uncontrolled proliferation results from mutations affecting proto-oncogenes (which become oncogenes) and tumour suppressor genes, which normally regulate the cell cycle.

Final Answer:
\(\text{Cancer is uncontrolled, invasive cell proliferation capable of metastasis to other body parts}\)