11/14/24, 10\:56 AM Malignant Melanoma of the Skin

Malignant Melanoma of the Skin

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A comprehensive topic overview

Introduction

Melanoma is a type of malignant cancer that arises from the melanocyte layer of the skin, normally situated in the basal
layer of the epidermis.
Melanoma is the
all other skin cancers combined.
2

Aetiology

Melanoma occurs when melanocytic stem cells undergo a genetic transformation and proliferate uncontrollably.
Melanocytes produce melanin, a protein that helps protect against harmful ultraviolet (UV) radiation exposure.
Melanocytes are found in equal numbers in di
damage caused by UV exposure is more likely in white skin compared to dark-brown or black skin.
1
The growth of melanoma can be described as follows\:
In situ\: the tumour is con
Invasive\: the tumour has spread into the dermis
Metastatic\: the tumour has spread to other tissues
When melanocytes grow in a non-cancerous way, they result in moles (benign melanocytic naevi) and freckles (lentigines
and phelides).
1,3

Subtypes of melanoma

There are four common subtypes of melanoma (Table 1).
Table 1. Common subtypes of melanoma.
1,3
Subtype of melanoma Description
Super
The most common type of melanoma.
Malignant melanoma cells have a longer ‘in situ’ phase (months to years).
Initially grows horizontally (known as the radial growth phase), presenting as
a
As invasion continues, the growth may become vertical.
Nodular melanoma
The most aggressive type of melanoma.
Malignant melanoma cells invade vertically, presenting as a nodule that
grows rapidly (weeks to months).
They often bleed or ulcerate.
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Lentigo maligna melanoma
Lentigo maligna is a precursor lesion to lentigo maligna melanoma and is
directly related to sun damage.
Lentigo maligna presents as a patch of discoloured skin that grows slowly
and becomes more atypical over time, often over years.
Acral lentiginous melanoma
A type of melanoma that originates on the palms, soles or under the nails,
presenting as a
Often diagnosed at a late stage due to their location.
Figure 1. Super
Figure 2. Nodular melanoma
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Figure 3. Lentigo melanoma
Figure 4. Acral lentiginous melanoma

Risk factors

Factors which increase the risk of melanoma include\:
2
History of skin cancer, melanoma, or atypical naevi
Family history of melanoma
Pale skin (Fitzpatrick skin type I and II)
Red or light-coloured hair
High freckle density
Light coloured eyes
History of sunburn
Sun exposure or tanning bed exposure
Large amounts of moles
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Increasing age
Immunosuppression
Outdoor occupation
Genetic syndromes with skin cancer predisposition (for example, xeroderma pigmentosum)

Clinical features

The
Patients commonly present with a change in shape, size or colour (including the loss of pigmentation) of a lesion. However,
melanomas can have no pigment (amelanotic melanoma), appearing as a pink or red lesion.
4,5
Important areas to cover in the history of a pigmented lesion include\:
Location of the lesion on the body
Date of onset of the lesion and duration
Size of the lesion
Changes in size, shape, and colour of the lesion
Any bleeding and/or ulceration
Risk factors
For more information, see the Geeky Medics guide to dermatological history taking.
ABCDE criteria
The ABCDE criteria are used to describe features that most melanomas have\:
1,5
A\: asymmetrical shape
B\: border irregularity, including poorly de
C\: colour change and variation
D\: diameter of the mole (most melanomas are >6mm)
E\: evolving (such as changing in size, shape or colour)
For more information, see the Geeky Medics OSCE guide to examining a pigmented skin lesion.

Di

Di
3
Benign naevus (mole)
Lentigines
Seborrhoeic keratoses
Dermato
Pigmented basal cell carcinoma (BCC)
Seborrhoeic keratoses
A common and benign class of lesion that can score highly on the ABCDE criteria are seborrhoeic keratoses (also
called seborrhoeic warts).
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Figure 5. Seborrhoeic keratosis

Investigations

Melanoma is
lateral margin of 2-3 mm. The diagnosis is con

Dermoscopy

The dermoscopic features of melanoma are highly variable and are assessed by trained physicians. In the early stages,
melanoma may appear with organised features. However, as time progresses, features become more disorganised.
Due to their melanocytic origin, melanomas have the following features on dermoscopy\:
6
Atypical network (white or pigmentated)
Aggregated black or brown dots and globules
Features speci

Investigations for metastasis

In patients with advanced melanoma (stage IIb+), investigations should be considered to assess for metastasis in other sites
of the body. Staging may be conducted with a whole-body and brain contrast-enhanced computed tomography
(CT) scan. Staging with brain magnetic resonance imaging (MRI) may be considered in special circumstances.
3,8

Management

All suspected melanomas should be referred urgently to a specialist. In the UK, an urgent referral means that you should
see a specialist within 2 weeks.
5
The management of melanoma depends on histological staging. Once a histological tissue sample is obtained, melanoma
can be staged accordingly.
Table 2. The staging of melanoma.
1
Stage Description
Stage 0‘In situ’ melanoma
Stage 1 Stage 2
Stage 3 Stage 4 Melanoma \< 2 mm in thickness
Melanoma > 2 mm in thickness, or > 1 mm in thickness with
ulceration
Melanoma spread to involve local lymph nodes
Metastases to distant sites
This is also known as the Breslow thickness, which measures the thickness of invasive melanoma in millimetres from the
granular cell layer to the deepest tumour cell.
1

Surgical management

The main management of melanoma is wide local excision. If the margins of the excised melanoma are inadequate, re-
excision is performed.
3,7
NICE guidelines recommend the following excision margins of tissue around the melanoma\:
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Stage 0 melanoma (melanoma in situ)\: at least 0.5 cm
Stage 1 melanoma\: at least 1 cm
Stage 2 melanoma\: at least 2 cm

Sentinel lymph node biopsy

A sentinel lymph node biopsy is a procedure to test for the spread of cancer. It is generally indicated for melanoma with a
Breslow thickness greater than 0.8 mm. It is often completed at the same time as surgical excision.
8
The presence of metastatic disease in the sentinel lymph node mandates additional surgery to remove the remaining
nodes, which is known as a lymph node dissection or completion lymphadenectomy.
8

Medical management

Targeted therapy such as dabrafenib and vemurafenib may be used in patients with BRAF V600 mutation-positivity.
Immunotherapy such as nivolumab plus ipilimumab may be given to patients with stage IV or unresectable stage III
melanoma if suitable.
Chemotherapy or the best supportive care may be considered for advanced melanoma not responsive to treatment.
3,8

Complications

Melanoma has the greatest potential for metastasis causing local tissue invasion and destruction as compared with other
skin malignancies.
Melanoma diagnosed at an advanced stage can cause serious morbidity and may be fatal despite treatment.
3,8
The prognosis of melanoma is determined by the stage of the skin cancer, taking into consideration the Breslow thickness,
spread to local lymphatics, and the level of ulceration.
The
95%. In comparison, the
is 7-19%.
3

Key points

Malignant melanoma is a cancerous neoplasm of the pigment-forming cells called melanocytes.
The rates of malignant melanoma are increasing, likely related to ultraviolet light exposure.
All suspicious pigmented lesions should undergo excisional biopsy for histology.
Management is dependent on the staging of melanoma. Surgical excision is the de
needed.

References

Dermnet NZ. M e l a n o m a . Published in October 2022. Available from\: [LINK]
The National Institute for Health and Care Excellence. M e l a n o m a . Available from\: [LINK]
Patient Professional. M a l i g n a n t M e l a n o m a o f t h e S k i n . Published in August 2022. Available from\: [LINK]
British Association of Dermatologists. M e l a n o m a S t a g e 2 . Published in February 2019. Available from\: [LINK]
Cancer Research UK. M e l a n o m a S k i n C a n c e r . Published in March 2020. Available from\: [LINK]
Dermnet NZ. D e r m o s c o p y o f m e l a n o m a . Published in 2008. Available from\: [LINK]
British Association of Dermatologists. D e r m a t o l o g y - A h a n d b o o k f o r m e d i c a l s t u d e n t s a n d j u n i o r d o c t o r s . November 2020. Available from\: [LINK]
Published in
The National Institute for Health and Care Excellence. M e l a n o m a \: a s s e s s m e n t a n d m a n a g e m e n t . Published in July 2015.
Available from\: [LINK]
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Image references

Figure 1. DermNet NZ. SuperCC BY-SA]
Figure 2. DermNet NZ. Nodular melanoma. Licence\: [CC BY-NC-ND]
Figure 3. DermNet NZ. Lentigo Maligna. Licence\: [CC BY-NC-ND]
Figure 4. DermNet NZ. Acral lentiginous melanoma. Licence\: [CC BY-NC-ND]
Figure 5\: Делфина. Adapted by Geeky Medics. Seborrhoeic keratosis. Licence\: [CC BY-SA]

Reviewer

Professor Nicola Ralph
Consultant Dermatologist

Acne vulgaris
Basal Cell Carcinoma (BCC)
Cellulitis
Cutaneous Squamous Cell Carcinoma (SCC)
Erythema Multiforme

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