What is Melanoma?
Melanoma is a cancer that arises in the melanocyte cells of the skin. Dr. Robert Carswell coined the term melanoma (melas – dark; oma- tumor) in 1938. Melanocytes are pigment-containing cells that give brown or tan color to the skin.
Melanoma can develop because of prolonged exposure to the sun or tanning beds. The ultraviolet (UV) rays damage the DNA of the skin over time and may thereby alter the normal functioning of the melanocytes. The risk of developing cancer due to the damaging UV rays is determined by the individual’s genes and the color of the skin. Melanoma is most often observed in adults. Melanoma in children is caused by either congenital moles that have become malignant or due to an inherited skin disorder (xeroderma pigmentosum).
Melanoma appears as an abnormal mole on certain regions of the body, such as the back, chest, legs, face, neck, or arms. Sometimes, an existing mole undergoes changes indicating a cancerous growth. The moles may either be brown, black, or with no dark color, such as tan, pink, or white. The cancer spreads to different parts of the body.
Depending on the site of occurrence, there are 3 types of melanoma:
Ocular melanoma – Melanoma that occurs in the melanocytes of the eyes is called ocular melanoma. It can be further subdivided into conjunctival melanoma and uveal melanoma.
Cutaneous melanoma – Melanoma that occurs in the skin is subdivided into 4 types:
- Nodular melanoma – This is an aggressive melanoma and accounts for ~ 15% to 30% of the melanoma cases. It is commonly observed in middle-aged people.
- Superficial spreading melanoma – This type of melanoma accounts for 70% of the melanoma cases and develops from an existing mole.
- Acral lentiginous melanoma – Unlike most other melanomas, this type of melanoma is more common in dark-skinned individuals. This type of melanoma is found below the nails, and on the palms and the soles of feet.
- Lentigo maligna melanoma – Such tumors are large and flat and observed in light-skinned women, people who have spent a lot of time outdoors, and in elderly people. These tumors occur on the face and do not spread much. They account for only approximately 10% of the cutaneous cases.
Mucosal melanoma – This type of tumor is difficult to detect and is found in the mucosal areas of the neck and head, the lower digestive and urinary tracts, and the vagina in females. They account for only 1% of all the cases of melanoma and patients with this type of cancer do not have a good survival rate.
Some of the risk factors for melanoma are:
- Presence of a large number of moles (more than a 100 normal moles) and changes in the moles – high risk
- Presence of atypical moles
- Family history (≥ 2 first-degree relatives with skin cancer)
- Presence of moles at birth (Congenital moles)
- Caucasian race
- Presence of a large number of freckles
- Skin that burns easily
- Frequent use of tanning beds before the age of 30
- Presence of blonde or red hair
- Weakened immune system, such as HIV, or use of medications that suppress immunity
- Exposure to certain chemicals
- Presence of any other skin cancer
- Older people
- Light skin that does not tan well
- Presence of blue eyes
- Prolonged exposure to sunlight
- Exposure to damaging ultraviolet rays
The symptoms of melanoma vary between individuals. A new mole or a noticeable change in an old mole should be considered as a warning sign to undergo further testing.
The ABCDEF acronym is used to clinically identify a melanoma.
A – Asymmetry of a mole
B – Irregularity of the borders of the mole
C – Color difference in the mole : Moles that change in color, become darker or show multiple colors should be suspected for the presence of melanoma
D – Diameter of the mole. Melanoma usually occurs in moles with a diameter of more than 6 mm
E – Evolving mole. A cancerous mole will show changes in height and width
F – Feeling around the mole. There may be a change in sensation around the mole.
For the initial diagnosis, a suspicious mole is examined with an instrument called the dermatoscope that is like a magnifying glass. Malignant melanoma is assessed by a biopsy. The entire lesion mole should ideally be removed with an adequate margin during biopsy.
Melanomas are also classified based on the degree of invasion (Clark’s Stages I- V) with the higher stages determining a greater degree of invasion. Stages I and II have a good survival rate while those with melanoma stage IIB or higher have a poor survival rate.
Additionally, liver function tests and a chest x-ray are obtained to detect any spread of the melanoma.
There are different ways to treat melanoma based on the stage of the disease.
Surgery: Tumors are excised with a 1-cm margin for a 1-mm thick lesion and a 2-cm margin for a 1 mm to 4 mm-thick tumor.
Lymph node removal: Lymph nodes surrounding the lesions are removed in patients below the age of 60 when the thickness of the tumor is in the range of 1 mm to 4 mm.
Sentinel lymph node biopsy is used to determine the degree of spread of the cancer to lymph nodes and the chances of survival of the patient. The sentinel lymph node is the first draining lymph node of the region and is identified using a radioactive tracer or a dye.
Vaccines: Patients may be treated with vaccines to stimulate the immune system. Immunotherapy with medications like pembrolizumab, nivolumab, and ipilimumab is also useful in treating melanomas. High dose interferon a2b has been used as adjuvant therapy for people at a high risk of relapse for the cancer following the surgical removal of the melanoma, but does not appear to improve overall survival.
Targeted therapy: Targeted therapy using BRAF inhibitors dabrafenib and vemurafenib and MEK inhibitors trametinib and cobimetinib have been found to be beneficial in the treatment of melanoma. A combination of dabrafenib and trametinib, and vemurafenib and cobimetinib has also been found to produce good response.
Chemotherapy: Drugs such as temozolomide, dacarbazine, a combination of dacarbazine, cisplatin, carmustine, and tamoxifen (DBCT), or cisplatin, vinblastine, and dacarbazine (CVD), are also used to treat melanoma. Chemotherapy is also sometimes combined with immunotherapy like interleukin 2 (IL-2) and interferon a2b (IFNa2b) in the treatment of melanoma.
Melanoma may be prevented if appropriate measures are taken. A prior history of melanoma places the individual at a greater risk.
- People who are at risk of getting melanoma should avoid the sun and protect their skin from getting burnt.
- They should expose very little skin by wearing protective clothing. Those who avoid the sun require vitamin D supplementation to make up for vitamin D deficiency.
- A broad spectrum sunscreen with sun protection factors (SPF) ranging between 20 and 30 should be used along with ultraviolet A (UVA) rating of 5 stars.
- The progress of the moles should be monitored with photography.
- Individuals who are at a high risk of getting melanoma should meet the dermatologist to learn about ways to self-examine themselves.
- Sunbeds and sunlamps should be avoided.
- What is melanoma skin cancer? - (http://www.cancer.org/cancer/skincancer-melanoma/detailedguide/melanoma-skin-cancer-what-is-melanoma)
- Melanoma Facts - (https://www.mdanderson.org/cancer-types/melanoma/melanoma-facts.html)
- Melanoma Symptoms - (https://www.mdanderson.org/cancer-types/melanoma/melanoma-symptoms.html)
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Latest Publications and Research on Melanoma
- Adjuvant dabrafenib plus trametinib versus placebo in patients with resected, BRAFV600-mutant, stage III melanoma (COMBI-AD): exploratory biomarker analyses from a randomised, phase 3 trial. - Published by PubMed
- An Integrated Analysis of the Safety of Tofacitinib in Psoriatic Arthritis across Phase III and Long-Term Extension Studies with Comparison to Real-World Observational Data. - Published by PubMed
- SEOM clinical guideline for secondary prevention (2019). - Published by PubMed
- M2-like polarization of THP-1 monocyte-derived macrophages under chronic iron overload. - Published by PubMed
- Adjuvant therapy for melanoma: how to choose? - Published by PubMed