Let’s repeat that Nodular melanoma is dangerous. Look out for a rapidly growing pink, red or brown nodule.
What are the clinical features?
The most common and best-known type of melanoma is superficial spreading melanoma (SSM), where the tumour cells spread horizontally in the upper layers of the skin. This type of melanoma accounts for 55-60% of melanoma and is the type most commonly seen in younger people. SSM is often found on the back in men and on the leg in women.
They can grow over months or years, particularly in the horizontal growth phase. The melanoma appears fairly flat and is usually pigmented.
Amelanotic means ‘no melanin’, and this type of melanoma appears to have no pigment, whilst hypomelanotic melanoma is partially pigmented. These unpigmented melanomas may have a pink, red, purple or normal skin colour appearance or be essentially clear and colourless.
As the name suggests, nodular melanoma is elevated and tend to be aggressive. Any ‘elevated, firm, growing’ lesion (EFG) needs to be taken seriously. Around half of nodular melanomas appear to have little or no pigment – they’re just pink or skin coloured growths – although around 90% of nodular melanoma seen through a dermatoscope does have some pigment.
The rule of thumb for nodular melanoma is to get any growing pink lesion that has not gone within a month checked out urgently
Lentigo Maligna is commonly found on sun exposed areas of the head and neck. This type of melanoma may be hard to spot on typically sun damaged skin because the melanoma tends to blend into the background look like a dirty-brown patch.
Lentigo maligna affects only the upper layer of skin (epidermis) and may grow for many years before growing down into the dermis when it is called lentigo maligna melanoma.
Acral Melanoma accounts for around 1-2% of melanoma in Australia. This type of melanoma is not related to sun exposure and occurs on the sole of the feet, palms of the hands, or nail-bed. Darker skin such as people of Asian or African descent are at greater risk.
This type of melanoma is rare and easily missed as it does not usually carry the normal warning signs. It tends to be felt as a firm lesion on the head or neck in older people. They may arise underneath a lentigo maligna.
What is the significance?
Why is Melanoma so important?
- Australia has the second-highest rate of melanoma in the world.
- The overall rate of melanoma in Australia has doubled in the last 34 years and is still increasing.
- Melanoma is the 4th most common cancer in Australia (other than the non-melanoma skin cancers).
- Most melanoma is caught at the curable stage.
- Melanoma can be easily mistaken for benign skin lesions.
Can I tell if I have a melanoma?
You can’t simply DIY whether a mole is harmless or not. Why? Because expert use of a dermatoscope is required to truly tell whether a mole is definitely harmless.
Around 65% of melanoma develop from scratch, whilst 35% develop from a pre-existing mole. In other words, you need to keep an eye out for both changing lesions as well as new lesions! This doesn’t help much, right?
Should you worry about every new lesion? Harmless moles continue to appear in Young to middle-aged adults, whilst adults from their 30’s can develop skin lesions like seborrhoeic keratosis and age spots (solar lentigo). Yet early melanoma can look like either of these lesions.
How can you evaluate change in a lesion? The famous ABCDE is a good starting point. A changing lesion is one that changes in either Asymmetry, Border, Colour, Diameter or is Evolving. In truth, any change is important. Melanoma may not be pigmented and may be entirely pink. The EFG rule was added later to help identify a dangerous type of melanoma called nodular melanoma.
Dermatoscopy examination has two benefits:
- A skin lesion that looks fine with the ‘naked eye’ may be concerning after dermoscopy.
- A skin lesion that might otherwise look ‘nasty’ may be entirely reassuring after dermoscopy.
The initial excision of a Melanoma is for diagnosis and staging, not for treatment.
The pathology report will indicate how dangerous the melanoma is. The single most important information is the ‘Breslow thickness. A measurement under 1mm is ‘good’ whilst >4mm is ‘bad’.
A melanoma will need re-excising after the initial biopsy.
It should be emphasized that the initial excision is for diagnostic purposes – even though the whole lesion will probably have been removed. A melanoma will require a second ‘definitive’ surgical procedure.
- Melanoma staging was last updated by The American Joint Committee on cancer (AJCC). Melanoma cancer classification is indicated by the initials TNM:
- T for tumour
- N for lymph nodes
- M for Metastases
Most melanoma is diagnosed at the curable stage. Let’s assume there is no lymph node involvement (N0) and no metastases (M0), and the Breslow thickness is <1mm. The tumour stage depends on Breslow thickness and the presence or absence of ulceration, giving the possibilities:
- Tis Melanoma in situ
- T1a <0.8mm thick without ulceration
- T1b <0.8 with ulceration, or 0.8 to 1mm without ulceration
- T2a >1 to 2mm without ulceration
- T2b >1 to 2mm with ulceration
Once you know The TNM classification, you can work out the staging.
- T1a is stage IA with a 95% 10 year survival.
- T1b or T2a is stage 1B with an 86% 10 year survival.
Melanoma has such a bad reputation that the diagnosis may come as a shock. However, melanoma diagnosed these days is usually curable.
Treatment will require further skin surgery in the form of a wide local excision (WLE). Tumour cells are spread beyond the visible margins, so the excision margins vary from 5mm to 2cm depending on the staging.
Local Recurrence of Melanoma
Melanoma cases diagnosed in Australia today have an excellent prognosis.
A ‘local recurrence’ can be implied by a melanoma that appears close to the original one. In other words, a new skin lesion near a scar from an excised melanoma might be a local recurrence.
There are two types of local recurrence:
- A true local recurrence where the original melanoma has grown immediately adjacent to the scar tissue. This is rare because original melanoma will have been cleared with generous margins as already described. Also, most local recurrences appear to lesions that are separate from the scar tissue.
- Microscopic lymphatic drainage to local skin
Therefore, a routine skin check will include a close examination of the skin next to the scar from a previously removed melanoma.
New drugs for advanced melanoma
Melanoma that was previously thought untreatable may now be treatable with drugs that target the immune system. A variety of immunotherapy is now available, targeting a specific aspect of the immune system – Interleukin 2, Interferon-alpha, and checkpoint inhibitors.
Immunotherapy is a major advance on traditional chemotherapy for metastatic melanoma.
Patients in Australia with advanced melanoma will typically be treated at their local ‘melanoma unit’, which is made up of melanoma specialists in pathology, plastic surgery, dermatology, oncology and radiotherapy.
These are some of the key terms that may be used a melanoma pathology report
Atypical Melanocytes don’t look normal eg. the nuclei look different.
The atypical melanocytes spread to the upper layer of the epidermis.
The distance between the granular layer of the epidermis and the deepest portion of melanoma.
The rate of mitoses of the melanoma cells (rate of Cell division)
The level of invasion
Lymphocytes are types of white blood cell involve in immunity. The melanoma cells may attract attention from the immune system in the form of tumour infiltrating lymphocytes.
Regression indicates loss of melanoma cells following attack by the immune system.
Neurotropism indicates a propensity to infiltrate the nerve tissue of the skin.
Lymphovascular Invasion refers to invasion of the lympatic or vascular vessels of the skin by melanoma cells.