What is cancer?

Cancer, in medical terms, is not a single illness but a constellation of diseases marked by the uncontrolled growth and spread of abnormal cells.

It can originate in any organ or tissue, form malignant tumors, invade adjacent structures, and sometimes disseminate through the bloodstream or lymphatic system to distant sites (metastasis).

Unlike benign growths, cancer cells can bypass the body’s regulatory checks and thrive, often acquiring distinct biological capabilities.

Understanding these core features is essential to grasp why cancer requires targeted interventions, early detection, and tailored treatments. 

What Is Cancer? 

At its core, cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body.

Cancer is not just one condition but a group of diseases where abnormal cells grow out of control and crowd out normal cells.

In medical language, cancer often refers to malignant tumors, masses of tissue formed by abnormal cells that can invade nearby structures and, in many cases, spread (“metastasize”) to distant organs. 

How Cancer Develops 

Cancer is fundamentally a genetic disease: changes to genes that regulate cell growth, division, and death lead cells to behave abnormally. These genetic alterations may arise from errors during normal cell division, inherited mutations passed down from our parents, or DNA damage caused by environmental factors such as tobacco smoke chemicals and ultraviolet radiation. Over time, as these mutations accumulate, the body’s capacity to eliminate or repair damaged cells diminishes, tipping the balance toward unchecked growth and survival of cells that should normally die. 

Hallmarks of Cancer Cells 

Cancer cells exploit a set of distinctive traits, often called “hallmarks”, that distinguish them from normal cells: 

• Sustained proliferative signaling: they grow even in the absence of external growth cues. 

• Evading growth suppressors and apoptosis: they ignore signals that normally tell cells to stop dividing or to die. 

• Tissue invasion and metastasis: they infiltrate neighboring tissues and can migrate to distant sites in the body. 

• Inducing angiogenesis: they stimulate new blood vessel formation, ensuring a steady supply of oxygen and nutrients. 

• Avoiding immune destruction: they hide from or manipulate the immune system to survive and grow. 

• Genomic instability: they accumulate chromosomal duplications, deletions, and other mutations at a high rate. 

Benign vs Malignant Tumors 

Not all abnormal cell growths are cancerous: benign tumors grow in a confined area, rarely invade other tissues, and usually don’t return once removed, whereas malignant tumors (cancers) invade surrounding structures, can recur, and may spread to form new tumors elsewhere. 

Why Understanding Cancer Matters 

Metastasis, the process by which cancer cells travel from their original site to distant organs, is the principal cause of cancer-related deaths. Many cancers, however, can be cured or effectively managed if detected early and treated appropriately, highlighting the critical importance of awareness, screening, and prompt medical intervention.