Melanoma Skin Cancer

Melanoma refers to a very serious type of skin cancer caused by the uncontrolled growth of melanocytes, also known as pigmented cells.

The outer layer of skin, known as a basal layer, contains normal melanocytes. Melanocytes produce melanin, a special protein that protects the skin cells by absorbing ultraviolet (UV) radiation. Non-cancerous growth of melanocytes results in the formation of moles and freckles on the body. However, the cancerous growth of melanocytes results in melanoma.

Typically, the onset of melanoma begins with an uncontrolled proliferation of melanocytic stem cells that have already undergone genetic transformation.

Risk Factors

Melanoma can affect any adult at any age. Even children are rarely affected. Melanoma is triggered by various factors, such as older age, family history of melanoma, Parkinson disease, presence of multiple irregular-looking naevi, and a large number of melanocytic naevi on the body. Individuals with white skin tend to burn much more easily. Even though individuals with white and black skin tend to have the same number of melanocytes, melanocytes found in black skin produce considerably more melanin. Therefore, individuals with darker skin are at lower risk of damage from UV radiation.

Location and Appearance

Melanoma can occur anywhere on the body, even on areas that were not exposed to the sun. It is usually considered a skin lesion. However, due to complications associated with this condition, it can also occur on the eye, mouth, or brain.

An unusual-looking mole or freckle may be suspicious for melanoma. Melanoma may appear in various colours, such as dark brown, black, red, light grey, and tan. During the horizontal growth phase, melanoma is usually flat. During the vertical growth phase, the lesion becomes more raised and thickened. Some melanomas can cause itching or bleeding.

Diagnostic Criteria

Initial screening is often based on the ABCDEs of melanoma or the Glasgow 7-point checklist. The ABCDEs scale represents the following criteria: A (Asymmetry), B (irregular Border), C (Colour change), D (Diameter of lesion exceeding 6 mm), and E (Evolving: changing and increasing in size).

The Glasgow 7-point checklist includes major and minor features relevant to diagnosis. Major features include a change in size, irregular shape, and irregular colour. Minor features include inflammation, a diameter of greater than 7 mm, oozing, and changes in sensation.

Classification

Generally, melanomas are classified according to their appearance and behaviour. Melanoma can also be classified based on its relationship with sun exposure, age, and number of melanocytic naevi. For example, early-onset melanoma is more prevalent in women than men. It is linked with a higher number of melanocytic naevi on the body and with irregular sun exposure. Late-onset melanomas are more prevalent in men than in women, with the head and neck being the most common sites. This type of lesion is linked with prolonged sun exposure.

Diagnosis

Melanoma is identified based on its clinical features or a history of lesion change. A dermatoscope is used to diagnose melanoma. Biopsies are also typically performed to confirm the diagnosis with a pathology report.

Treatment

Melanomas are removed completely through surgical excision. In rare cases where melanoma has spread widely throughout the body, the surgical method may not always be successful. In such cases, some patients may be offered experimental treatment methods such as immunotherapy and PD-1 blocking antibodies.

Follow-Up Care

Patients who have had melanoma are typically scheduled for follow-up appointments with their dermatologist to examine the scar where the initial melanoma was excised and to conduct additional skin examinations to reduce further risk. Patients with more advanced primary disease may be scheduled for regular blood tests and imaging, including X-ray, CT, MRI, and ultrasound. Additional testing is not prescribed to patients with stage 1 or stage 2 melanoma, nor is it indicated for individuals who have remained healthy for more than five years following the removal of their melanoma.