Definition and Overview
Melanoma is a type of skin cancer that starts in the cells that produce melanin. Melanin is the pigment that gives the skin, hair, and eyes their colour.
Melanoma can develop in any part of the body. However, it is most common in body parts that are often exposed to the sun. These include the chest, back, and legs. It can also develop on the foot or ankle.
The disease is one of the least common types of skin cancers, but it is the most dangerous. It accounts for just less than 1% of all skin cancer cases but is responsible for the most number of skin cancer-related deaths. This is because it tends to spread to other parts of the body.
Up to 15% of melanoma cases occur on the foot. It can develop on the sole and even under the toenails. The disease has a high mortality rate because it is often detected when it has already reached a more advanced stage. Treatment is often challenging when cancer has already spread to vital organs.
Causes of Condition
Malignant melanoma of the foot is often caused by prolonged exposure to ultraviolet (UV) rays from the sun or tanning beds. UV rays can damage the skin cells’ DNA and cause them to grow and divide uncontrollably. This is how cancer develops.
Other factors that can increase the risk of the disease include:
A history of severe sunburns - Most patients with skin cancer have a history of blistering sunburn when they were younger.
Having a fair skin - Many cases of skin cancer are seen in people with a fair complexion. Many of them also have blue eyes and red or blond hair.
A history of skin cancer - People who have had any type of skin cancer has a higher-than-average risk of the disease. As such, patients who received skin cancer treatment in the past are advised to make regular follow-ups with their doctors. This is key to diagnosing recurrences in the early stages when cancer is most responsive to treatment.
Weakened immune system - Having a weak immune system makes a person more prone to many disorders and diseases, including skin cancers.
Certain inherited conditions - A number of rare inherited conditions are found to increase the risk of skin cancer. These include hereditary ovarian and breast cancer syndromes.
Malignant melanomas have irregular shapes and borders. They also have a mix of colours and grow over time. Because they can develop on the sole of the foot and on the nail bed, they are often overlooked. Because of this, doctors advise patients to do a self-exam at least once a month. This is especially helpful for those who have risk factors listed above.
Patients must also remove their nail polish from time to time to make sure that there is no abnormal growth on their nail beds.
Who to See and Types of Treatments Available
Patients with abnormal-looking moles must immediately consult a skin specialist (dermatologist). Early diagnosis gives patients the best chance of getting cured. When caught early, skin cancer can be removed with a simple outpatient procedure.
To diagnose the condition, the doctor will start by physical examining the abnormal growth. The patient is then asked a few questions about it. The doctor would want to know when it developed and if its appearance has changed since. The patient is also asked about his or her medical history. The physical exam is followed by dermatoscopy. This test uses a special magnifying lens and a light source. It can determine if the growth is benign or malignant. If test results suggest that it is malignant, the doctor will order a biopsy before making a diagnosis.
A skin biopsy involves removing the skin cancer so it can be studied under a microscope. If this test confirms foot melanoma, the doctor will perform another biopsy. The goal of the second biopsy is to see if the cancer has already spread beyond the foot. The doctor may use a fine needle to remove small pieces of nearby lymph nodes. This can also be done with open surgery. Imaging tests are also used to assess the extent of cancer spread. These tests often include an MRI and PET and CT scans. These tests create detailed images of the organs in the body. Thus, doctors are able to easily spot any abnormalities.
Treatment of the disease depends on its severity. Stage 0 melanoma can be treated with surgery alone. The entire growth can be removed if it is limited to one location. Stages I and II of the disease are more serious but often not deadly. These stages mean that cancer has possibly spread to the deeper layers of the skin. Although more challenging, they can still be cured in many cases.
Stages III and IV melanoma are often life-threatening. These stages mean that cancer has already spread to nearby lymph nodes, surrounding structures, and other parts of the body. The most common sites of spread are the lungs, bone, brain, and abdominal organs.
Surgery is the main treatment for the disease. Its goal is to remove the entire tumour and a small margin of healthy tissues surrounding it. In some cases, the surrounding lymph nodes are also removed. To ensure that no cancer cells remain after surgery, patients also often undergo chemotherapy and radiation therapy. They may also be placed on immunotherapy, which aims to strengthen the immune system.
If the disease has reached the advanced stages, it may not be possible for surgeons to remove the entire tumour. In such cases, treatment is often supportive in nature. This means that the patient is treated mainly to relieve his or her symptoms. The five-year survival rate for patients with stage IV melanoma is only 15-20%. Patients have a slightly better outlook if cancer affects just the distant parts of the skin and not the internal organs.
Gershenwald JE, Morton DL, Thompson JF, et al, Collaborators of the AJCC/UICC Melanoma Task Force. Staging and Prognostic Factors for Stage IV Melanoma: Initial Results of an American Joint Committee on Cancer (AJCC) International Evidence-based Assessment of 4,895 Melanoma Patients. J Clin Oncol. 2008;26(May 20 suppl; abstr 9035). Abstract presented at American Society of Clinical Oncology (ASCO) 2008 Annual Meeting.
Norris W. Eight cases of Melanosis with pathological and therapeutical remarks on that disease. London: Longman; 1857.