Melanoma is a malignant skin tumour of melanocytic origin, the most aggressive form of skin cancer. It is a tumour that forms from melanocytes, the cells that produce the pigment melanin, which is the basis for our skin colour. About 50% of melanomas arise from nevi, and 50% can occur in perfectly healthy skin. Around 200 new cases of melanoma are diagnosed in Lithuania every year, and as many as two thirds of these are in women. Unfortunately, melanoma is usually diagnosed at stage II or even IV. Although it is the least common of all skin cancers, the incidence of melanoma is rising worldwide, by around 7-8% each year. The 5-year survival rate depends on the stage of the disease at diagnosis. Melanoma is the form of skin cancer with the fastest spread and highest mortality.
What factors increase the likelihood of developing melanoma?
- Ultraviolet rays. The risk is increased not only by excessive exposure to the sun’s natural rays, but also by sunbathing in solariums and childhood sunburn. People with fair skin (especially those who burn quickly) have a higher risk of sunburn because their skin is not particularly resistant to the damaging effects of UV rays.
- Pigmented skin type: fair skin, fair hair, blue eyes, tendency to freckles. These people burn quickly in the sun. All of these factors, which are indicative of increased sensitivity of the skin to sunlight, are risk factors for melanoma.
- High number of body moles (> 50). Although most melanomas occur on smooth skin, it is advisable to examine your own moles for possible changes at least once a month.
- Atypical moles. These are benign, acquired melanocytic moles that have some of the features of melanoma, e.g. they may be asymmetrical, irregularly contoured, multi-coloured etc. The risk of melanoma increases if a person has a large number of atypical moles or a family history of melanoma. For more information, see atypical moles.
- Heredity. About 10% of melanoma cases are genetic. The risk increases considerably if the melanoma patients have first- or second-degree relatives.
- The patient has a history of non-pigmented skin cancer.
- Immunosuppression (after organ transplantation, cancer, HIV infection, long-term use of corticosteroids). In these patients, melanoma occurs in healthy skin.
Signs of melanoma
Melanoma can arise from a mole (congenital or acquired), as well as on smooth skin, where the tumour is formed by melanocytes that are not grouped into a mole. Melanoma usually develops within a few years, but there are also very aggressive forms, where the tumour grows rapidly and reaches a thickness of several millimetres within three months. In 90% of cases, melanoma is found in the skin, in 8% in other organs, and in 2% of cases, no primary melanoma is found and only distant metastases are identified.
Most melanomas arise as superficial skin tumours that do not cross the epidermal barrier for many years and do not spread to the deeper layers of the skin. This is the so-called “horizontal” phase of growth. At this stage, melanoma is most amenable to surgical treatment. Once the tumour has begun to spread deeper into the lower layers of the skin, the ‘vertical’ phase of growth begins. Such tumours can metastasize to distant organs such as the lungs, liver, brain and bones.
ABCDE melanoma detection method
It is important to know that changes in the size, shape and colour of a mole are warning signs of melanoma. The ABCDE method is the easiest way to identify the warning signs of melanoma:
- A (asymmetry) – the mole is asymmetrical, with different shapes on either side;
- B (edges) – the edges of the mole are jagged, irregular or indistinct;
- C (colour) – black, brown shades, white, grey, red or blue streaks may be visible;
- D (diameter) – usually more than 6 mm in diameter, or a tumour similar in size to an eraser at the end of a pencil (or larger). However, in the case of melanoma, the tumour may be smaller when first detected;
- E (evolution) – the size, shape, colour or appearance of the mole changes, or the mole starts to grow in healthy skin. Any change in the size, shape, colour or prominence of a skin spot, or any new symptoms such as bleeding, itching or crusting, may be a warning sign of melanoma.
If any of these symptoms or signs are of concern, be sure to talk to your doctor. The earlier melanoma is detected, the more likely it is that treatment will be successful.
There are 4 main subtypes of melanoma:
- Surface spreading melanoma. This is the most common subtype of melanoma, found in about 70% of all melanoma cases. In two-thirds of cases, it is a newly formed tumour in healthy skin. It has been observed that superficial melanoma is most common in men on the back and in women on the lower legs. It is characterised by a patch or thin plaque of variable colour and irregular borders. The size may range from a few millimetres to centimetres. The tumour may have a reddish, bluish, black or grey tinge.
- Nodular melanoma. The second most common subtype of melanoma, accounting for 15-30% of all melanoma cases. It is characterised by a dark-coloured nodule, which may resemble a polyp, with a ‘leg’. The colour is uniform, sometimes with a reddish tinge.
- Malignant slag (lentigo maligna). Most often occurs in older people in sun-damaged areas. The disease starts as a brown spot which grows larger and darker over the years, with asymmetry, unevenness of colour and relief. It accounts for 10 – 15% of all melanoma cases.
- Acrolentiginous melanoma, accounting for <5% of all melanoma cases. Affects the skin of the palms and soles of the hands, the submental areas. A dark brown or black spot or plaque with surface irregularities appears. Occasionally ulcerated and bleeding. Ponagic melanoma originates in the growth zone of the nail and manifests as a longitudinal dark streak in the nail plate. A dark ulcerated mass may also appear under the nail.
Early diagnosis of melanoma is the key to improving the survival prognosis of patients. For more information on melanoma diagnosis, see Early diagnosis of melanoma.