Metastasis is the process of cancer spreading throughout the body. It starts when cancer cells from a primary tumor infiltrate surrounding healthy tissue. As the cells multiply, they can spread by one of three routes: transcoelomic, lymphatic, or hematogenous spread.
Malignant cells infiltrate the covering surfaces of cavities in our bodies during transcoelomic spread. The peritoneum is a set of surfaces that serve as walls to divide the body cavity. In ovarian cancer, for example, malignant cells travel through the peritoneum, which connects the ovary to the liver, resulting in metastasis on the liver surface.
Cancerous cells then enter the blood vessels as a result of hematogenous spread. Malignant cells make use of the fact that there are blood vessels practically everywhere in the body to reach more distant portions of the body.
Finally, lymphatic spread happens when cancer invades lymph nodes and spreads through the lymphatic system to other regions of the body. This system provides a vast network for cancer because it drains numerous regions of the body. Furthermore, lymphatic veins empty into the bloodstream, allowing malignant cells to spread via the bloodstream.
The cells proliferate again once they reach a new location, forming little tumors known as micrometastases. The metastatic process is completed when these tiny tumors grow into full-fledged tumors.
Specific locations of metastasis have been identified in various malignancies. Prostate cancer, for example, frequently metastasizes to the bone, whereas colon cancer metastasizes to the liver. Several theories have been offered to explain the pattern of malignant cell migration. Two opposing views are particularly intriguing.
The seed and soil theory of metastasis was proposed by Stephen Paget, an English surgeon. According to the seed and soil idea, cancer cells die quickly in the wrong microenvironment; therefore, they only spread to places with similar features.
The seed and soil idea was disputed by James Ewing, the first professor of pathology at Cornell University, who claimed that the position of the arterial and lymphatic pathways draining the initial tumor influenced the place of metastasis. Patients with initial tumors drained by arteries leading to the lungs developed lung metastases over time.
We now know that both ideas contain significant truths. The complete story of metastasis, however, is far more convoluted than either of the proposed theories.
We can discover ways to stop the process by researching both genetic and environmental factors that contribute to effective metastasis. The fight against cancer is never-ending, and scientists are constantly working on novel ways to combat metastasis.
Immunotherapy, which involves using the immune system’s power to eliminate migratory cells, has recently gained popularity. This can be accomplished in a variety of ways, including by using vaccinations to train immune cells to recognize malignant cells. Injecting man-made interleukins, substances that are normally generated by the body’s immune cells, can also promote immune cell growth and activity. This is merely the tip of the iceberg in terms of treatments. Perhaps, with the combined research efforts of governments, businesses, and scientists, the process of metastasis will be permanently halted.
