Melanoma is a form of skin cancer, originating from melanocytes, the cells responsible for producing skin pigment. A significant concern with melanoma is its ability to metastasize, a process where cancer cells break away from the original tumor and spread to other parts of the body.
Understanding Metastasis
Melanoma cells can detach from the primary tumor and spread through the body. This spread, known as metastasis, occurs when cancer cells invade surrounding tissues and enter either the lymphatic system or the bloodstream. Once within these systems, they can travel to distant locations.
The lymphatic system acts as a primary pathway for melanoma spread. Cells can enter lymph vessels located near the primary tumor and travel to regional lymph nodes. These lymph nodes serve as filters, and cancer cells can become trapped and begin to grow there. A different route for dissemination is through the bloodstream, a process called hematogenous spread. Melanoma cells can invade blood vessels, circulating throughout the body and potentially settling in distant organs where they can form new tumors.
Common Metastasis Sites
Melanoma often spreads to specific areas. The first and most common sites are usually the regional lymph nodes. These nodes are part of the lymphatic system, which drains fluid from tissues, making them a natural first stop for migrating cancer cells.
Beyond the lymph nodes, melanoma can also spread to other areas of the skin and subcutaneous tissue, which is the layer directly beneath the skin. This includes “in-transit” metastases, which are new lesions that appear between the original tumor site and the nearest group of lymph nodes. Distant skin metastases can also occur, appearing as new nodules or bumps on the skin far from the initial melanoma.
The lungs are a frequent distant site for melanoma metastasis. This is largely due to the continuous flow of blood through the lungs, making them a common destination for cancer cells traveling via the bloodstream. Similarly, the liver is another common organ for distant spread. Its rich blood supply and role in filtering blood make it susceptible to circulating melanoma cells.
The brain is a common site for melanoma metastasis, occurring in approximately 40-50% of patients with advanced disease. While less common than spread to the lungs or liver, melanoma can also metastasize to bones. This can lead to localized pain or an increased risk of fractures from minimal trauma. Melanoma has the potential to spread to almost any organ, including the gastrointestinal tract, heart, pancreas, adrenal glands, kidneys, and spleen, but the previously mentioned sites are observed with greater frequency.
Recognizing Signs of Spread
If melanoma has spread to the lymph nodes, people may notice swelling or lumps in areas where lymph nodes are concentrated, such as the neck, armpits, or groin. These swollen nodes can sometimes be tender or painful.
When melanoma spreads to the skin or subcutaneous tissue, new nodules or bumps may appear. These can be fast-growing, black or red spots that might bleed or break open.
If melanoma has spread to the lungs, a persistent cough, shortness of breath, or chest pain may develop. Some individuals might even cough up blood. These symptoms arise as the growing tumors interfere with normal lung function.
Melanoma metastasis to the liver can manifest as abdominal pain, particularly on the right side, or unexplained weight loss. Other signs can include jaundice, a yellowing of the skin or eyes, and generalized itching. Swelling in the abdomen or legs may also occur.
Spread to the brain can lead to a variety of neurological symptoms. These can include persistent headaches, seizures, changes in vision, or even alterations in personality or memory problems. Weakness or numbness in parts of the body might also be experienced.
When melanoma metastasizes to the bones, localized bone pain is a common symptom. This pain can be severe and may sometimes be accompanied by fever. In some instances, bones may become weaker and prone to fractures with minimal trauma.
Beyond these site-specific signs, general symptoms of advanced cancer, such as fatigue, unexplained weight loss, or loss of appetite, can also indicate melanoma has spread.