In cancer biology, metastasis refers to which process involving the spread of cancer cells in the body?

Introduction:
Cancer becomes especially dangerous when it spreads beyond its original site to other parts of the body. This spread is responsible for many of the severe complications and deaths associated with malignant tumours. The technical term for this spreading process is metastasis. This question checks whether you can correctly define metastasis and distinguish it from other cellular processes such as normal mitosis or growth inhibition.

Given Data / Assumptions:
- The keyword in the question is metastasis. - Options describe different cellular processes, including rapid division, spread of cells, chromosome movements and inhibition of division. - We assume a basic understanding of how cancers behave in the body. - The focus is on the behaviour of cancer cells, not normal cells.

Concept / Approach:
Metastasis is the process by which cancer cells break away from the original (primary) tumour, enter blood vessels or lymphatic vessels, travel through the circulation and establish new tumours (secondary tumours) in distant organs such as lungs, liver, bones or brain. This distinguishes malignant tumours from benign ones, which do not spread in this way. Processes like normal mitosis, chromosome attachment to the spindle and complete inhibition of division are unrelated to metastasis. Therefore, the correct description of metastasis is the spread of cancer cells through blood or lymphatic systems to other sites.

Step-by-Step Solution:
Step 1: Identify metastasis as a feature of malignant cancers, not of normal cell division. Step 2: Recall that metastatic cancer cells invade surrounding tissues and penetrate lymphatic or blood vessels. Step 3: Understand that they travel via these vessels to distant parts of the body and can form secondary tumours there. Step 4: Compare this process with normal mitosis and chromosome movements, which occur in healthy cells and are not specific to cancer. Step 5: Recognise that complete inhibition of cell division is the opposite of tumour growth and does not describe metastasis. Step 6: Choose the option that clearly mentions cancer cells spreading through blood or lymphatic systems to other organs.

Verification / Alternative check:
Oncology textbooks and cancer awareness resources describe metastasis as the spread of cancer from the primary site to distant parts of the body through blood or lymph. They often provide examples, such as breast cancer metastasising to bones or lung cancer to the brain. Pathology diagrams show how tumour cells detach, invade vessels, circulate and colonise new tissues. Meanwhile, basic cell biology texts define mitosis and chromosome behaviour in non cancerous terms, and therapies aim at inhibiting division, not describing it. These references confirm that the spread of cancer cells via blood or lymph fits the definition of metastasis.

Why Other Options Are Wrong:
Normal body cells dividing rapidly under the influence of growth promoting drugs: This describes stimulated cell division but not the movement of cancer cells to distant organs. Chromosomes attaching to the spindle before moving to opposite poles in anaphase: This is a normal step in mitosis and meiosis, not specifically related to cancer spread. Cancer cells being completely inhibited so that they can no longer divide: This would describe successful treatment or cell cycle arrest, not metastasis.

Common Pitfalls:
Learners sometimes confuse metastasis with rapid local growth of a tumour, thinking any increase in size is metastasis. Others mix up technical terms from mitosis, such as spindle or anaphase, with cancer processes because both are studied in cell biology. To avoid confusion, remember that metastasis always involves movement of cancer cells to new locations via blood or lymph, resulting in secondary tumours away from the original site.

Final Answer:
Metastasis is the process in which Cancer cells spread through the blood or lymphatic system to distant sites or organs and form secondary tumours.