Melanoma: Different Forms & Characteristics

Introduction to Malignant Melanoma:

Melanoma is the most dangerous type of skin cancer, this cancer develops from melanocytes, which are the cells that produce melanin and are found in the basal layer. One of the most common causes of skin cancer is exposure to UV radiation from the sun. Overexposure results in damage to the DNA, when the DNA is damaged and is allowed to multiplicate mutations make occur which cause skin cells to replicate rapidly forming a tumor.

Melanomas usually resemble moles and as such, it is very easy to mistake one for the other, though they do have some key difference which helps to identify whether it's a melanoma or not. This is crucial as in its early stages it is almost always curable, which makes it a lot more important that practitioners know how to identify it. If it is able to be diagnosed early it may save a person’s life. There are 4 primary types of malignant melanomas, these being Nodular melanoma, Lentigo maligna melanoma, Acral lentiginous melanoma, and superficial spreading melanoma. Melanomas don’t always look the same which makes it important for practitioners to know all the different ways they can look.

Melanoma in Situ:

If the melanoma is diagnosed early there is a chance that the melanoma is still in situ. This is the earliest stage and it means that the cancer cells haven’t spread around the body yet and are still confined to the area where they started to develop. This is the most important time to make a correct diagnosis as the cancer cells are still localized. If some skin is suspected to have a malignant growth (due to showing some symptoms of a melanoma), the entire affected area would be removed by a process called excision and if the area is too big an incision biopsy will be taken. The sample is then examined under a microscope and a pathology report will be made which will help to plan the next step if it is found to be malignant.

Distinguishing Factors Between Benign and Malignant Moles:

Moles are very common and are usually benign but in some cases, they can evolve or change. There are a couple of warning signs for melanoma that differentiate them from benign moles. The warning signs are known as the ABCDE rules. These are Asymmetry, Border irregularity, Colour variation, a large Diameter, and Evolving. Normal moles are usually symmetrical while malignant moles are usually asymmetrical in shape. A benign mole usually has a defined smooth even border. In the case of melanoma, the borders tend to be uneven and notched edges. Benign moles usually have the same colour all around, usually, a shade of brown, malignant moles may have multiple shades of brown and black. It can also become a shade of red or white. The diameter of moles is also smaller than that of melanoma, its diameter can be as large as 6mm, though they may have been smaller when initially detected. Over time melanomas start to evolve and change. It is important that if the person notices any changes, they are reported immediately as this isn’t exhibited with normal benign moles.

Superficial Spreading Melanoma:

This is the most common type of skin cancer, making up around 70% of all cases. This melanoma grows on the top layer of the skin until eventually, it penetrates deeper into the skin though it usually takes months. It usually appears as a flat or slightly raised patch of skin with irregular borders and an asymmetrical shape. It may appear as a variety of colours including, red, blue, black and brown. Figure 2 shows how different the same type of melanoma can look. This type of melanoma has a chance to develop from a previously benign mole, though it may develop as a new lesion and not necessarily on a mole. This type of melanoma first has a stage of horizontal growth which means that initially, it looks like a discoloured slowly enlarging flat area of skin. It is very often mistaken for a mole, lentigo or freckles. When a patient is suspected to have superficial spreading melanoma (SSM) the practitioner can diagnose the melanoma using a skin biopsy or dermoscopy. If the suspected melanoma is 0.8 mm thick a blood test and a lymph node biopsy are advised. In the pathology report, there will be the following if melanoma is present. There should be, the rate of proliferation, the Breslow's thickness and Clark level invasion which shows the anatomical plane of invasion (the deeper the Clark level is the greater the risk).

The report may also have the cell type, growth pattern and whether the disease is in-situ or associated with an original mole. (These steps are always necessary to confirm the presence of cancerous cells). People with darker skin have a smaller chance of getting melanoma, it is as common in men as it is in a woman and only 15% of people get melanoma before the age of 40 and only 1% of people get it before the age of 20. Other things that may put a person at risk is, having a lot of moles, having easily burned skin and previously having melanoma.

Nodular Melanoma:

Nodular melanoma grows vertically instead of horizontally like SSM. It can arise from normal-looking skin or from an already existing melanoma, it can develop from superficial spreading melanoma if the malignant cells cross the epidermis into the dermis. Within a few months, it can penetrate deep into the skin. People with Nodular melanoma (NM) tend to have fair skin and tend to tan easily, as opposed to people with darker skin who are less prone to getting it. Though there is a stronger correlation with sun exposure and SSM and Lentigo than with Nodular melanoma. An increase in age, any previous cases of melanoma and having a lot of moles or birthmarks. The melanoma can develop anywhere though there is a higher chance of it appearing on exposed areas of the skin. Nodular melanoma sometimes doesn’t follow the ABCD rules in its early stages as it is typically symmetrical in shape, has regular borders, uniform colours and has a relatively small diameter (less than 6mm) because of this, the EFG rule has to be used.

The EFG summarises the clinical features of NM, these are elevation, firm on palpation and constant growth over a month. It is important that during history taking the patient can give any information about the lesion in question. In this case, the lesion may bleed or change in elevation, therefore these questions must be asked to the patient to see if he has observed those changes. Under normal circumstances, the NM will follow the ABCD rule and will be asymmetrical, have irregular borders, a large diameter (larger than a mole) and may have different colours like black, brown or red. The melanomas seen in figure 3 all follow the rule.

Lentigo Maligna Melanoma:

Lentigo maligna melanoma (LMM) is an invasive skin cancer that develops from lentigo maligna. Lentigo maligna is confined to the epidermis and thus stays on the other surface of the skin. It is only when the lentigo maligna invades the dermis layer that LMM is diagnosed. The chance of this happening is very low, around 5%. The number increase if the lesion is larger than 4cm, in which case the chance goes up to 50%. Usually, people that work outside in the sun, people with fair skin and the elderly have a higher chance of getting lentigo maligna. Males also have a higher chance of getting it, but this may be due to sun exposure due to their work. Areas on the body that are normally exposed to the sun, especially the face and nose have a greater chance of being affected. Lentigo maligna grows slowly were as LMM spreads very quickly and aggressively. Lentigo maligna and LLM also share a very similar appearance but it is important that the practitioner can distinguish them. Figures 4 and 5 show how easy it is to mistake one for the other. The ABCDE rule can be used but they both share the same characteristics as they are both asymmetrical, have irregular borders, they have abnormal colour variation (dark brown-red or pink), have a large radius and evolve.

There are only a few characteristics that they don't share, these being that the lesion can start bleeding, and itching, it may start to thicken, and it may exhibit some abnormal colours like blue or black. Figure 4: This is the presentation of LLM://www.dermnetnz.org/topics/lentigo-maligna-and-lentigo-maligna-melanoma/ In a study conducted by lentigo like melanomas have a high chance of being identified by the patients themselves, the dermatologists also recognized this kind of lesion as being malignant, especially when they have their typical appearance. Patients with this kind of melanoma usually have sever dermatoheliosis (up to 30%) and also have a history of sunburns (up to 90%). This data could help practitioners to make a correlation with the patient’s history and the lesion being presented to them.

Acral Lentiginous Melanoma:

Acral lentiginous Melanoma (ALM) is the only type of melanoma mentioned that has no correlation with exposure to the sun, as the areas where ALM appears aren’t typically exposed to the sun. In a study conducted by Al-Hassani, F., Chang, C., Peach, H., they came to the conclusion that this type of melanoma is connected with microtrauma, more specifically, trauma on weight-bearing areas as that is where the highest concentration of ALM was found (83.5% of it was found on the weight-bearing areas of the foot). ALM typically affects the palms and soles but is more frequently seen on the feet. In its early stages, it looks like a flat patch of slowly expanding discoloured skin. Initially, it stays in the epidermis, which is the tissue of origin of ALM, but as months go by it starts expanding and eventually becomes invasive (which is when the dermis is penetrated). ALM is relatively rare in comparison with the other melanomas, there is no correlation between the skin colour and the rate of occurrence. Since skin colour doesn’t affect ALM there is a higher chance that a person with darker skin gets this type of melanoma as they have a lower chance of getting the other types. ALM can be recognised by the ABCDE rule as it is asymmetrical, has irregular borders, it has an abnormal colour, it has a large diameter and it evolves. Figure 6 shows these characteristics.

Conclusion:

As has been discussed above melanoma can present itself in different forms and all exhibit different characteristics. It is important that practitioners are able to identify and diagnoses these lesions as early as possible to ensure the best outcome for the patient. The practitioner may try to identify the lesion my its appearance by following the ABCDE method, the Dermatoscope is very useful in order to examine these lesions. It allows for the practitioner to have a closer and thus more detailed look at the presenting lesion. After the practitioner makes his decision after making a diagnosis a biopsy or a tissue sample is taken, to confirm whether the lesion id malignant or not. After which the proper steps are taken to remove the malignancy if the lesion is confirmed to be malignant by the biopsy.

References:

1. Al-Hassani, F., Chang, C., Peach, H., (2017) “Acral lentiginous melanoma- Is inflammation the missing link?” JPRAS Open, Volume 14, pages 49-54
2. British Association of Dermatologists. (November 2011) “Melanoma in situ”, retrieved January 3, 2019, from: http://www.bad.org.uk/shared/get-file.ashx?id=2126&itemtype=document
3. Klebanov, N., Gunasekera, N.S., & Lin, W.M. (2018). Clinical spectrum of cutaneous melanoma morphology. Journal of the American Academy of Dermatology.
4. Oakley, A, Dr. (2011). “Acral lentiginous melanoma” Retrieved January 4, 2019, from https://www.dermnetnz.org/topics/acral-lentiginous-melanoma/
5. Oakley, A, Dr. (2011). Lentigo maligna and lentigo maligna melanoma. Retrieved January 4, 2019, from https://www.dermnetnz.org/topics/lentigo-maligna-and-lentigo-maligna-melanoma/
6. Oakley, A, Dr. (2011). Nodular melanoma. Retrieved January 4, 2019, from https://www.dermnetnz.org/topics/nodular-melanoma/
7. Oakley, A., Dr. (2011). Superficial spreading melanoma. Retrieved January 4, 2019, from https://www.dermnetnz.org/topics/superficial-spreading-melanoma/
8. Sara Kalkhoran, BS; Olivia Milne, MBBS; Iris Zalaudek, MD; et al (2010). Historical, Clinical, and Dermoscopic Characteristics of Thin Nodular Melanoma,
9. Skin Cancer Foundation . Retrieved January 3, 2019, from: https://www.skincancer.org/skin-cancer-information/melanoma#panel1-2