Melanoma Development
Melanomas are derived from melanocytes, cells within the skin that are responsible for making the protein melanin, the main pigment within the skin. Melanoma develops when the melanocytes develop genetic mutations which cause them to grow abnormally quickly and to stop responding to signals from other cells that tell them to stop growing. Typically these mutations are a result of DNA damage that arises from sun exposure, though they can also occur from the skin being damaged by corrosive chemicals or from burns. In some cases, these genetic problems are hereditary, meaning that they were present from birth. The UV rays from the sun are able to penetrate the cells and damage their DNA. If enough DNA damage occurs, it causes genetic changes in the cells, causing them to become cancerous. Over time, melanomas may develop genetic changes that allow them to leave the skin tissue and travel to other tissues, making them malignant.
Melanoma Growth
Melanomas typically have two different growth phases, which are termed radial and vertical. Melanomas begin with the radial growth phase, which means that they grow horizontally throughout the skin. This causes the melanocytes to spread out and proliferate, but they stay at the same depth throughout the outer portion of the skin, known as the epidermis. Over time, however, melanocytes begin to grow vertically, which allows them to penetrate deeper and deeper within the skin. This lets the melanocytes get into the deeper layer of the skin, which is known as the dermis. When melanocytes penetrate into the dermis they then can escape from the skin.
Malignant Melanoma Spread
The spread of malignant melanomas depends on the cancer developing the ability to escape the skin tissue and then form new tumors elsewhere in the body. To escape the skin tissue, melanomas use proteins called matrix metalloproteinases. These proteins have the ability to break down the extracellular matrix which is what holds healthy cells together and keeps them in place. Once this matrix has been broken down, the melanocytes are able to travel throughout the body, often migrating to the lymph nodes. Once the malignant melanoma has traveled to a lymph node, it will then release chemical signals which allow the cancer to make new blood vessels so that it can be supplied with oxygen and nutrients.
