Melanoma is an aggressive form of skin cancer that develops from the pigment-producing cells known as melanocytes. When these cells become malignant, they proliferate rapidly and invade surrounding tissues. Melanoma has a significant capacity to spread to distant parts of the body, making early detection and immediate treatment crucial for patient outcome. Ignoring a melanoma diagnosis allows the cancer to progress unchecked, transforming a potentially curable localized tumor into a systemic and fatal disease.
Initial Local Progression
The first consequence of untreated melanoma is the deepening of the tumor into the skin layers. Melanoma initially grows outward in the radial growth phase, where cells are confined to the uppermost layer of the skin, the epidermis. This phase may last for months or years, and if the tumor is removed during this period, the cure rate is very high.
Without treatment, the tumor transitions into the vertical growth phase, penetrating the basement membrane and invading the deeper layer of the skin, the dermis. This downward invasion is measured as the Breslow thickness, which is a powerful indicator of the tumor’s future behavior. Once the cancer cells breach the dermis, they gain access to the network of blood vessels and lymphatic channels. This access allows the malignant cells to exit the primary site and begin the process of metastasis.
Regional Lymph Node Involvement
After invading the dermis, the lymphatic system often serves as the initial route for cancer cells to travel to other parts of the body. The lymphatic pathways drain fluid and cells from the skin to nearby lymph nodes, which function as biological filtering stations. The first lymph nodes encountered are the regional lymph nodes.
When untreated, melanoma cells become trapped and multiply within these nodes, establishing secondary tumor deposits. The presence of cancer in the regional lymph nodes significantly worsens the patient’s outlook compared to a strictly localized disease. These nodes act as a staging area for further dissemination. Melanoma cells passing through the lymphatic system may also become more resistant to cell death, enhancing their ability to spread to distant organs.
Systemic Consequences of Advanced Disease
Once the cancer cells bypass the regional lymph nodes and enter the bloodstream, the disease becomes systemic, leading to distant metastasis. This advanced stage is characterized by the colonization of vital organs throughout the body. The most common sites for this distant spread include the lungs, liver, brain, and bones.
Lungs and Liver
Metastasis to the lungs is a frequent occurrence. Symptoms arising from lung involvement can include a persistent cough, chest pain, and shortness of breath due to tumors obstructing airways or fluid accumulating around the lungs. The liver is another common target due to its function in filtering blood. Tumors there cause symptoms such as loss of appetite, abdominal pain, and jaundice (a yellowing of the skin and eyes).
Brain and Bones
Melanoma has a notable tendency to spread to the central nervous system, with brain metastases occurring in a substantial portion of patients. Tumors growing in the brain can cause severe neurological symptoms, including persistent headaches, seizures, changes in vision, and cognitive dysfunction. Spread to the bones results in bone pain, an increased risk of fractures, and changes in bowel or bladder function. These systemic consequences lead to profound physical deterioration and organ failure that define end-stage, untreated melanoma.
Untreated Prognosis and Mortality
Allowing melanoma to progress untreated leads to a predictable and severe outcome. As the disease transitions from a localized lesion to one involving distant organs, the prognosis shifts from a high likelihood of cure to a certainty of death. Early-stage melanoma is highly treatable, with a five-year survival rate near 99% for localized disease.
Once the cancer has spread to distant sites, the outlook changes dramatically, even with treatment. For a patient with untreated metastatic melanoma, the disease is universally fatal. Life expectancy in this advanced stage often ranges from less than a year to a few years, depending on the tumor’s aggressiveness and the organs involved. The relentless growth of cancer in these vital organs eventually compromises their function, leading to organ failure and death.