A malignant growth refers to an abnormal and uncontrolled proliferation of cells within the body. These growths pose significant health risks because of their aggressive nature. This process involves cells dividing without the usual regulatory mechanisms that keep cell growth in check.
Characteristics of Malignant Growth
Malignant growths exhibit several defining features at both cellular and tissue levels. One hallmark is uncontrolled proliferation, where cells divide rapidly and without regulation, surpassing the normal limits of cell division. This leads to an increased number of cells in a tissue, often forming a mass.
Another characteristic is the loss of differentiation, also known as anaplasia. Malignant cells lose their specialized functions and resemble immature, less specialized cells, which is reflected in their altered appearance under a microscope. Their nuclei often become larger and irregularly shaped, with prominent nucleoli, and the ratio of the nucleus to the cytoplasm increases.
Malignant cells also demonstrate invasiveness, meaning they can penetrate and grow into surrounding normal tissues. Additionally, these growths can stimulate angiogenesis, the formation of new blood vessels, to ensure a continuous supply of nutrients and oxygen to support their rapid growth.
Genomic instability is a further defining feature, involving the accumulation of genetic mutations within the cells. These mutations can affect genes that control cell growth, division, and repair, contributing to the uncontrolled proliferation and other malignant characteristics. The presence of numerous and often abnormal cell divisions, known as atypical mitoses, further indicates malignancy.
Distinguishing Malignant from Benign Growths
Understanding the differences between malignant and benign growths is important for assessing their potential impact on health. Malignant growths typically exhibit a faster growth rate compared to benign growths, which tend to grow slowly and remain stable over time.
A key distinction lies in their boundaries and invasiveness. Benign growths often have clear, smooth, and well-defined borders, and they are frequently encapsulated by normal cells. Conversely, malignant growths rarely have distinct encapsulations; instead, they possess irregular, jagged borders and can invade and destroy surrounding tissues.
Differentiation levels also vary significantly; benign growths are generally well-differentiated, meaning their cells closely resemble the normal cells of the tissue from which they originated. In contrast, malignant growths are poorly differentiated or anaplastic, with cells that have lost their specialized features. This lack of differentiation contributes to their aggressive behavior.
A defining feature of malignant growths is their potential for metastasis, the ability to spread to distant parts of the body. Benign growths do not metastasize and remain localized to their primary site. Consequently, malignant growths are more likely to recur even after treatment, especially if not entirely removed, whereas benign growths are less likely to return once excised.
How Malignant Growth Spreads
The spread of malignant growth, known as metastasis, is a complex, multi-step process that accounts for a large percentage of cancer-related deaths. It begins with local invasion, where cancer cells break away from the primary tumor and penetrate into adjacent normal tissues. These cells are less “sticky” than normal cells, which helps them detach and move more easily.
Following local invasion, malignant cells can undergo intravasation, where they enter nearby blood vessels or lymphatic vessels. This entry allows them to travel throughout the body.
Once inside the bloodstream or lymphatic system, these cells circulate, potentially traveling to distant sites. Surviving cells eventually undergo extravasation, exiting the vessels into new tissues at a distant location.
Upon reaching a new tissue, the cells must then colonize and grow, establishing a secondary tumor. This involves finding ways to thrive in their new environment, often by inducing angiogenesis to secure a new blood supply to support their proliferation. Common sites for metastasis include the lungs, liver, bones, and brain, although specific types of cancer tend to spread to particular organs.