Melanoma and lentigo maligna

Latest update 28/09/2010

This chapter is set out as follows:

• Incidence and aetiology
• Who is at risk & management of risk factors
• Giving advice to patients
  • Self-examination and what to look for
  • General images of moles and melanoma
  • Sun protection and vitamin D3
• Who to refer
• When should family members be referred?
• Dermoscopy of melanoma
• Histology - including melanocytic lesions of unknown malignant potential
• Management of melanoma - resources
• Melanoma - pregnancy and hormonal medications
  
• Types of melanoma:
  
  • Melanoma in situ and superficial spreading melanoma
  • Nodular melanoma
  • Lentigo maligna and lentigo maligna melanoma
  • Acral-lentiginous melanoma
  • Amelanotic melanoma
  • Metastatic melanoma

Incidence and aetiology

Incidence

• Over the last thirty years, the incidence of melanoma has increased more than for any other common cancer in the UK. Rates in males have increased more than five times since 1978, while in females they have more than tripled. 10,672 new cases were diagnosed in 2007
• The lifetime risk of developing melanoma is 1 in 91 for men and 1 in 77 for women in the UK
• Age - although rates are highest in the over 70s, there is a substantial number of cases in younger patients. 30% of all cases arise in people aged less than 50 years and in the 15-34 age-group melanoma is the most common cancer (when non-melanoma skin cancers are excluded). Melanoma is extremely rare pre-puberty
• Site - over 1/3 of male cases arise on the trunk, particularly the back, while the most common site in females is on the legs

Aetiology

• Environment - the association between melanoma and sun exposure is complex. In the case of superficial spreading melanoma there does appear to be an association with intermittent sun exposure especially in childhood, for nodular melanoma the picture is less clear. In lentigo maligna melanoma the risk is increased by the total number of lifetime hours of sun exposure
• Genetics - it is likely that there is a genetic spectrum of inheritance for melanoma ranging from more common low-penetrance genes (the majority of people carrying these genes will not develop the disease) to rare high-penetrance genes (the majority of people carrying these genes will develop the disease if they live long enough)

Who is at risk & management of risk factors

Slightly increased risk (1-3 times that of the general population)

• Risk factors
  • Skin that burns easily
  • Red or blond hair
  • A high density of freckles
  • Any family history of melanoma

• Management
  • Give advice (see section below)

Moderately increased risk (8-10 times that of the general population)

• Risk factors
  • Large numbers of moles, some of which may be atypical in appearance (atypical melanocytic naevi)
  • A personal history of melanoma
  • Organ transplant recipients

• Management - patients with large numbers of moles of which some are atypical should be referred to a dermatologist for assessment and photography, otherwise:
  • Counsel about the risk
  • Give advice (see section below)
  • Patients should examine themselves once a month

High-risk (more than 10 times that of the general population)

• Risk factors
  • Patients with giant congenital melanocytic naevi
  • Those with a strong family history (see section on which family members should be referred)

• Management
  • Refer. Long-term dermatology follow-up needed

Giving advice to patients

Self-examination

• While everyone should examine their own skin from time to time, those at moderate or high-risk should examine themselves once a month. It is important to have a way of assessing the back, backs of legs - this is easiest performed by a partner/relative
• For the purpose of self-examination patients may wish to keep pictures of their moles for comparison. They may do this themselves or they may have photographs provided for them e.g. patients will lots of moles, especially if some are atypical should be referred to dermatology for assessement and photography

What patients should be told to look for

1. Patients should be asked to report new or old + changing moles that show the features listed below in point 2
   
   
2. In terms of specific advice for moles I use a slight variation from the original ABCD rule:
   
   
   • Asymmetry of features i.e. one half is different to the other in terms of shape and/or colour
   • Border irregularity - notched, uneven or blurred
   • Colour variation - the colour is different to their other moles OR the mole has different colours or shades of colour
   • Dimension - persistant growth in a mole (there are exceptions e.g. moles growing symmetrically through puberty are very likely to be normal, as are moles that become raised up, are soft and wobbly to palpate and maintain a symmetrical shape)
     
     
3. Ugly ducking - melanoma can present in many different ways, and there are different types of skin cancer. One of the most important aspects of self-examinaton is for the patient to be familar with all of their lesions, such that any new or old + changing skin lesion that looks or behaves differently (e.g. history of bleeding) to the rest should be reported

General images of moles and melanoma

It is extremely useful to show pictures of normal moles and melanoma to help demonstarte the points above - the images shown below can be used for this purpose, patients can access these images themselves if they wish

	Figure 1 - Multiple benign melanocytic naevi All moles symmetrical in terms of both shape and colour (copied with kind permission from Dermatoweb)
	Figure 2 - Benign melanocytic naevus Even shape. Symmetrical distribution of colour - two shades of brown, slightly darker in the centre and lighter at the edge
	Figure 3 - Benign melanocytic naevus Dark brown centre, lighter periphery. Shape shows a minor degree of asymmetry, however there was no history of change in this long-term mole and it remained unchanged at follow up
	Figure 4 - Benign melanocytic naevus A very regular shape with an even border. Two colours present, which are both shades of brown -  the colour is distributed in a very organised, symmetrical fashion
	Figure 5 - Benign melanocytic naevus Very symmetrical in terms of shape and colour. Colour fades to the edge
	Figure 6 - Benign melanocytic naevus Symmetrical. Although elevated in the centre the lesion was very soft and wobbly to palpate, which is reassuring. In younger patients a change from a flat mole to one that becomes elevated in this way is relatively common
	Figure 7 - Benign melanocytic naevi Symmetrical in shape and colour. Soft and wobbly to palpate
	Figure 8 - Benign melanocytic naevus Symmetrical. Two colours, lighter at the edge. Soft and wobbly
	Figure 9 - Melanoma in situ A - asymmetry of shape B - uneven, jagged border C - black colour, different to patients other moles D (dimension) - growth
	Figure 10 - Superficial spreading melanoma A - asymmetry of shape and colour distribution B - notched border C - black and brown colours D - growth
	Figure 11 - Superficial spreading melanoma A - asymmetry of shape and colour distribution B - border very irregular D - growth
	Figure 12 - Supeficial spreading melanoma A - Highly asymmetrical lesion B - border very irregular C - different shades of brown and red D - growth
	Figure 13 - Superficial spreading melanoma A - asymmetry of shape and colour distribution  B - irregular border C - black, red and brown colours D - growth
	Figure 14 - Superficial spreading melanoma The fact that a lesion is very small does not discount a diagnosis of melanoma: A - asymmetry of shape and colour distribution B - jagged border C - 3 colours (black, dark brown and light brown) D - growth
	Figure 15 - Superficial spreading melanoma A - asymmetry of shape and colour distribution B - irregular border with notching C - 3 colours (black, brown and red)  D - growth
	Figure 16 - Superficial spreading melanoma Three colours and asymmetry
	Figure 17 - Superficial spreading melanoma Asymmetrical pink and brown colours - pink is not a colour to be overlooked as it can respresent an amelanotic component of a melanoma A - asymmetry of shape and colour distribution B - irregular notched border C - colour. Pink and brown, different to patients other moles D - growth
	Figure 18 - Nodular melanoma The lesion follows the A,B,C,D rules and is nodular
	Figure 19 - Amelanotic melanoma presenting as an ugly duckling At first glance this looks like a BCC however it was not entirely typical and dermoscopy did not reveal any of the usual features. Any pink or red nodule that cannot be clearly identified as benign must be regarded with a high index of suspicion
	Figure 20 - Amelanotic melanoma presenting as an ugly duckling This was a new firm nodule. It could not be readily identified and was different to anything else on the patients skin - an ugly duckling. Histology showed a melanoma - their is no room for observing and following up solitary nodules of unknown aetiology

• Make educational resources available to patients by having posters and information leaflets in GP waiting rooms and other appropriate settings
• Organise local education events and open them up to GPs, practice nurses, poditarists and those who have contact with the most vunerable such as district nurses and staff working in nursing/other care homes

Who to refer

Melanoma is as likely to arise de-novo as it is from a pre-existing mole. One of the difficulties in assessing a patient with skin lesions is the history. Depending on site and number of moles it can be difficult to be certain whether or not a particular mole is new, whether or not a pre-existing mole has changed, and if a mole is new or has changed is it continuing to grow?

Moles more likely to be benign:

• Those growing gradually and symmetrically through puberty
• Brown moles that gradually become domed shaped and soft/wobbly to palpate while maintaining a regular symmetrical edge
• Colour - brown moles that are one colour, or two colours where the colours are similar (e.g. two shades of brown) AND where the pigment is arranged in a symmetrical fashion e.g darker centre and lighter edge
• Itchy moles that are not changing and otherwise appear normal
• Moles that change rapidly (over a few days) becoming swollen, inflammed and crusty AND which then settle back down to their original appearance - these moles are likely to have been traumatised or become acutely infected. Such patients must be followed up after 2-3 weeks to make sure that the symptoms are settling, if not the patient should be referred as a two-week wait
• Classical halo naevi - for more information on how to differentiate between a halo naevus and a regressing melanoma please follow the link

The following should be regarded as suspicious and referred urgently to secondary care (normally dermatology but check local pathways) as a two-week wait:

• Shape - any mole that has lost its symmetry
• Colour:
  • Any mole that has 3 or more colours
  • Any new or old + changing mole which has two or more colours with an uneven distribution of pigment
  • Any new mole which differs in colour to a patients other moles e.g. black, pink or any other unusual colour
• Growth:
  • Persistant growth of either a new mole that arises after puberty OR new growth in any long-standing mole. Lesions that grow persistantly need referring even if they are symmetrical in shape and colour (the only exception to this rule is those lesions that become domed shaped and soft/wobbly to palpate while maintaining a regular symmetrical edge such as the naevus in figure 7 above)
  • Sometimes it is difficult to know whether or not a mole has grown and whether or not it is continuing to grow. If the lesion is flat and looks otherwise normal the mole can be photographed and the patient reviewed 3 months later, if there is evidence of ongoing change at review or before then, the patient should be referred. There is no place for observation of solitary nodules and plaques (see below)
• Bleeding moles without a history of trauma - even with a history of trauma if the bleeding does not settle or the mole looks abnormal it should still be referred
• Nodules and plaques - any new solitary nodule or plaque where a benign diagnosis (e.g. dermatofibroma) cannot be made with confidence. 50% of nodular melanomas are hypo/amelanotic and so may present as a red-pink elevated lesion
• Nails - a new pigmented line in a nail or unexplained destruction of a nail
• Mucosal surfaces - any new or old + changing pigmented lesion on the lips or other mucosal surfaces
• Relevant dermoscopic features – see later

Other patients that would benefit from non-urgent referral to dermatology for assessment, baseline photography and education on self examination:

• Patients with large numbers of moles, especially if some are atypical

When should family members be referred?

• 3 or more cases of melanoma or pancreatic cancer
• 2 cases of melanoma in a family PLUS any of the following:
  • the presence of multiple primary melanomas in one of the affected individuals
  • the presence of multiple atypical moles
• Family members should be referred routinely to a clinic managing inherited predisposition to cancer (involving dermatologists and/or clinical geneticists)

Dermoscopy of melanoma

Dermoscopy is a learning curve and appropriate education is needed. In the first instance it should be used to aid the diagnosis of benign skin lesions such as seborrheoic keratoses, blue naevi, dermatofibroma and angioma - in the right hands dermoscopy can reduce the number of unnecessary excisions/referrals for lesions that turn out to be benign

The use of dermoscopy to help assess melanocytic lesions requires considerably more experience. Although a number of algorithms exist they should not be viewed in black and white as they all have flaws. The list below provides a brief insight in to some of the different dermoscopic presentations of melanoma - for more information please refer to the dermoscopic section of the website

Suspicous dermoscopic findings include:

• An atypical pigment network
• A negative pigment network
• While we recommend that all spitzoid lesions should be referred for excision those with asymmetrical streaks are more likely to be malignant
• A blue-white veil
• Blue / white structures - please refer to the dermoscopic section of the website
• Melanocytic lesions with an asymmetrical arrangement of dots/globules, especially if their is some involvement of the periphery
• A muticomponent pattern, especially if associated with asymmetry of structures
• A pigment blotch that is peripheral or enlarging
• A partially pigmented or amelanotic lesion with a milky red hue or areas with atypical blood vessels (e.g. irregular vessels, dot vessels)
• Lesions with an uncertain diagnosis following clinical / dermoscopic examination i.e. unspecific, featureless tumours
• Beware thick tumours as they may lack dermoscopic criteria
• A lesion showing significant dermoscopic change on follow-up
• Melanocytic lesions on the palms & soles, face and mucosal surfaces take on different dermoscopic appearances - see later in this chapter for more information

Beware - even if the dermoscopic appearance appears normal, if the history or naked-eye examination is suspicious the patient should still be referred as a two-week wait

Histology

• Lesions suspicious of melanoma should not be removed in the community. Any lesion found by chance to be melanoma must be referred urgently to secondary care as a two-week wait
  
• Histological interpretation of melanocytic lesions is not always straightforward:
  • It can be difficult to distinguish between dysplastic naevi and melanoma. To this end all lesions histologically found to be 'dysplastic' must be completely excised
  • Melanocytic lesions of unknown malignant potential - this is a term reserved for cases where there is histological uncertainty around whether or not the lesion is a melanoma. Patients should be managed as per a suspected melanoma and referred to secondary care as a two-week wait. Such cases should have their histology reviewed at the MDT meeting to try and decide whether or not the lesion is a melanoma, before then deceiding on further management

Managment of melanoma - resources

• Melanoma must only be managed in secondary care and so cases of suspected melanoma must be referred urgently as a two-week wait
• For more in-depth guidance please refer to:
  • The NICE guidelines Improving Outcomes for People with Skin Tumours including Melanoma
  • The Concise Guidelines to Good Practice - developed by the melanoma study group

Melanoma - pregnancy and hormonal medications

• Pregnancy - there is no evidence that melanoma at or around the time of pregnancy affects the outcome for mother or baby, but the social and family effects of developing recurrent melanoma during pregnancy or after birth are great and so appropriate counselling is needed
• The COCP - there is no evidence that this plays any role in the natural history of melanoma
• HRT - there is no evidence that this plays any role in the natural histroy of melanoma, neither does it worsen the prognosis in stage I or II melanoma

Diagnosis: Melanoma in situ and superficial spreading melanoma

Key diagnostic features:

• Superficial spreading melanoma account for 50% of all UK melanomas and show a female preponderance
• Slow growing lesions initially, which develop horizontally at first for a few months (melanoma in situ) before they have the capacity to become invasive (superficial spreading melanoma)
• Distribution - commonest on the lower leg but can occur anywhere
• Appearance:
  • Colour – flat and predominantly dark brown or black and may be variegated
  • Shape - the outline becomes more irregular as the lesion grows and may have a pink-red halo
  • A nodule developing within a lesion signifies deep dermal invasion

	Figure 1 – Early superficial spreading melanoma Early de-novo lesions can be small. This 4mm lesion demonstrates irregular shape and pigmentation
	Figure 2– Superficial spreading melanoma Asymmetry and multiple colours – red, brown and black. Three colours is always suspicous
	Figure 3 – Superficial spreading melanoma Irregular edge and uneven distribution of pigment
	Figure 4 -Superficial spreading melanoma with a deeply invasive component This elderly patient had developed the lesion several years prior to presenting - she gave a story that it had developed following a knock to the shin The superficial component is very irregular (black arrow). The deep component is a nodule (red arrow) that had developed much later
	Figure 5 – Superficial spreading melanoma Which is the melanoma? Beware of lesions that stand out from the others. In this image the melanoma (black arrow) is darker and has an irregular shape when compared with the other lesions
	Figure 6 – Dermoscopic appearance of figure 5 A multi-component lesion with a central homogenous zone (black arrow), dots (red arrow) and an asymmetrical pigment network that is much more evident at the periphery (blue arrow)
	Figure 7 – Melanoma in Situ
	Figure 8 – Dermoscopic view of figure 7 Atypical pigment network (arrow) and irregular pigmentation
	Figure 9 – Superficial spreading melanoma Notched edge and irregular distribution of pigment
	Figure 10 – Dermoscopic appearance of figure 9 Atypical pigment network with several asymmetrical areas of thickened network with irregular meshes. Irregular streaks (black arrow) and irregular distribution of pigment (red arrow)
	Figure 11 – Melanoma in situ Irregular shape and uneven distribution of colour
	Figure 12 – Dermoscopic appearance of figure 11 A collection of dots and globules at one edge - the lesion is very asymmetrical
	Figure 13 – Superficial spreading melanoma on lower leg Three colours, irregular edge
	Figure 14 – Dermoscopic appearance of figure 13 Varying sized dots and globules (black arrows) and a blue-white veil (red arrows)
	Figure 15 – Superficial spreading melanoma Unusual colourings and asymmetrical
	Figure 16 – Dermoscopic appearance of figure 15 The features are more subtle than in figures 11 & 13, nevertheless the irregularity of the dots & globules (black arrow) in terms of size, colour and distribution is suspicous
	Figure 17 – Melanoma-in-situ A dark blotch at the edge of a lesion raises the index of suspicion (arrow)
	Figure 18 – Dermoscopic appearance of figure 17 This lesion did not score 3 or more on 7-point checklist. However a pigment blotch at one edge (black arrow) should always raise suspicion. Most of the lesion is red-skin colour (red arrow)
	Figure 19 – Superficial spreading melanoma of the ear
	Figure 20 – Dermoscopic appearance of figure 19 Pigment blotch at the periphery (red arrow), irregular distribution of dots
	Figure 21 – Melanoma in situ This lesion was reported as recently changing with the development of a notched edge
	Figure 22 – Dermoscopic image of figure 21 showing a negative pigment network Pigment networks are normally brown. In this case the network appears white (black arrows) and is termed a negative pigment network. Although this does not score highly on the 7-point check list, such a pattern is very suspicious
	Figure 23 – Superficial spreading melanoma left thigh The presence of three colours in a lesion is always suspicous. This lesion is brown, black and red
	Figure 24 – Dermoscopic appearance of figure 23 A negative pigment network (red arrow), and an abnormal vascular pattern with a central milky red hue (black arrow)
	Figure 25 – Superficial spreading melanoma Red, brown and black. Irregular shape
	Figure 26 – Dermoscopic appearance of figure 25 The combination of a featureless lesion and a milky red colour (left lower quadrant) is very suspicous
	Figure 27 – Superficial spreading melanoma Irregular shape and colour
	Figure 28 – Dermoscopic appearance of figure 27 Again a large featureless area (red arrow) with a milky red hue (black arrow)
	Figure 29 – Melanoma, Clark's level 4
	Figure 30 – Dermoscopic appearance of figure 29 A relatively subtle melanoma that does not score highly on the 7-point checklist The clues to the diagnosis was a changing lesion in a patient aged 63 and a relatively featureless lesion with some irregularly distributed dots (black arrow) and pigmentation (red arrow)
	Figure 31 – Recurrent melanoma This patient had a melanocytic lesion removed a few years earlier - it had not been sent for histology. The white areas are from the previous surgery All melanocytic lesions that are removed must be sent for histology even if clinicaly they appear benign
	Figure 32 – Dermoscopic appearance of figure 31 Atypical pigment network (red arrows) and irregular streaks (green arrow)

Diagnosis: Nodular melanoma

Key diagnostic features:

• Account for 20-25% of cases of melanoma and are the most aggressive type
• Grow more rapidly with vertical growth phase (having capacity for invasion) from the beginning
• More common in males and often present in the 5th or 6th decade
• Distribution - can arise anywhere but most common on sun-exposed areas
• Appearance
  • Nodular
  • Predominantly dark brown or black, and may be variegated. Up to 50% are hypo/amelanotic
  • Ulceration and bleeding are common

	Figure 1 - Nodular melanoma Dense black irregular lesion with multiple nodular components
	Figure 2 – Dermoscopic view of figure 1 Atypical pigment streaks (black arrow) and blue-white veil (red arrows)
	Figure 3 -Nodular melanoma
	Figure 4 - Melanoma, dermoscopic appearance of figure 5 Just because a lesion has milia-like cysts does not mean that it must be a seborrhoeic keratoses. When making a diagnosis it is crucial to take into account the history, examination and dermoscopic appearance. The clinical appearance of this lesion (figure 5) was highly suspicious and so the lesion was excised with a 2mm margin
	Figure 5 - Melanoma with nodular component

Diagnosis: Lentigo maligna and lentigo maligna melanoma

Key diagnostic features:

• Tend to arise in later middle age and elderly patients
• Distribution - sun exposed areas, especially the face
• Appearance:
  • Colour - flat, dark brown or black and may be variegated
  • Shape - irregular
• Dermoscopy - see below
• Lesions grow steadily over a number of years and eventually develop in to lentigo maligna melanoma, the change is seen clinically when a nodule arises from within a lesion

Dermoscopy and the face

The structures of the facial epidermis differ to those on the trunk as the rete ridges (epidermal projections in to the dermis) are flat or absent, and their is an increased number of hair follicle units. As a result lesions may lack a conventional pigment network found at other sites and so it can be diffcult differentiating between the various lesions that can take on a similar clincial appearance e.g. solar lentigines, seborrhoeic keratoses, benign lichenoid keratoses and lentigo maligna

I) Solar lentigines / early seborrheoic keratoses

• Yellow opaque areas
• Fingerprint-like structures
• A sharply defined moth-eaten border
• A pseudonetwork with a broad 'rounded' mesh and holes created by the numerous pigment free hair follicles and openings of sweat glands
• Milia-like cysts
• Thicker seborrhoeic keratoses also have comedo-like openings
• Obliteration of hair follicles

II) Lentigo maligna tend to develop progressive features as follows:

• Short fine streaks and slate-gray dots appear around the follicles producing an annular-granular pattern. The density of pigmentation shows greater asymmetry compared to benign lichenoid keratoses
• Asymmetrical hyperpigmentation of the hair follicles (as the abnormal cells descend into the follicles)
• Rhomboidal-like structures develop as the streaks become larger and intersect - these tend to be angulated
• As the hyperpigmented areas coalesce the lesion may become homogenous and blue-grey

III) Benign lichenoid keratoses have a grey granular pigmentation that is evenly distributed. Asymmetrical hyperpigmentation of hair follicles is absent. These lesions are harmless

Additional notes

• Suspected and confirmed cases of lentigo maligna and lentigo maligna melanoma needed to be referred urgently under the two-week rule to secondary care
• Diagnosis - smaller lesions can be be excised. This is impractical for larger lesions where instead diagnostic punch biopsies are taken from the most atypical looking area of the lesion
• Histology can miss an early lentigo maligna, and so facial lesions with a 'benign' histology but showing atypical pigmentation need to be closely monitored

	Figure 1 - Solar lentigo of left cheek An evenly coloured brown patch
	Figure 2 - Dermoscopic appearance of figure 1 Homogenous yellow-brown colour with a 'moth-eaten' border (arrow)
	Figure 3 - Solar lentigo left cheek
	Figure 4 - Dermsocopic apperance of figure 3 A pseudonetwork is seen where the hair follicles disrupt the yellow/brown pigmentation. This 'network' is more rounded (arrows) compared with the angulated network seen in lentigo maligna
	Figure 5 - Solar lentigo of forehead
	Figure 6 - Dermoscopic appearance of figure 5 A rather rounded (arrow) pseudonetwork. No evidence of irregular pigmentation of hair follicles
	Figure 7 – Lentigo maligna right cheek
	Figure 8 – Dermoscopic view of figure 7 Irregular pigmentation / destruction of hair follicles (black arrows)
	Figure 9 – Lentigo maligna left cheek
	Figure 10 – Dermoscopic view of figure 9 Early lesions show multiple dots (black arrows) and streaks that are starting to develop an annular-granular pattern and are irregularly distributed
	Figure 11 – Lentigo maligna of nose Note irregular shape and asymmetry
	Figure 12 – Dermoscopic image of figure 11 Lentigo maligna develop networks with a rhomboidal pattern (black arrow), which is angulated
	Figure 13 – Close up of a lentigo maligna
	Figure 14 – Dermoscopic view of figure 13 Rhomboidal structures are very well developed in this case (black arrows)
	Figure 15 – Lentigo maligna melanoma This lesion grew for many years as lentigo maligna before an invasive nodular component developed (arrow)
	Figure 16 – Dermoscopic appearance of a lentigo maligna Destruction of hair follicles
	Figure 17 - Benign lichenoid keratoses Granular pigmentaion that is evenly distributed. No evidence of irregular pigmentation of hair follicles. Rhomboidal structures absent

Diagnosis: Acral-lentiginous melanoma

Key diagnostic features:

• Rare in caucasions, but relatively much more common in people from the Far East
• Initially they can present as deceptively banal-looking pigmented macular areas, hence the term lentiginous. With time, however, raised, densely black nodular areas develop within this macular area of pigmentation
• A sub-group arising around the nails are known as subungual melanoma. These are most commonly found around the big toe and thumb. They present as a painless growth expanding under the nail. They are often black but may be amelanotic. The following can be found on examination:
  • Expansion of pigment onto the nail fold (Hutchinson's sign)
  • No progression in colour that you would expect to see with trauma
  • Melanonychia striata which is a longitudinal band of pigment that grows longitudinally and may widen, with no proximal sparing over time
  • Ulceration and destruction of the nail plate (whereas fungi cause thickening, onycholysis and subungual hyperkeratoses)

Dermoscopic features on the palms and soles of acral lesions

The anatomy of the skin differs in the palms and soles with a parallel arrangment of the skin surface markings known as the dermatoglyphics, which run straight or in whorls. These surface markings are composed of parallel gyri (ridges) and sulci (furrows). Openings of the eccrine sweat ducts (acrosiringium) are found in the centre of the ridges

Benign melanocytic lesions demostrate pigmentation in the narrower sulci that is termed a parallel-furrow pattern and is best demonstrated on the peri-weight bearing areas. The acrosiringium are not affected. Additional patterns found in benign naevi are the lattice-like pattern (pigmentation following and crossing the furrows, most commonly seen on the instep), and the fibrillar pattern (numerous fine pigmented filaments perpendicular to the furrows, most commonly seen on weight bearing areas)

In melanoma a number of patterns can be found

• The parallel-ridge pattern - pigmentation seen in the wider gyri, acrosiringium are affected. The pattern may be obscured in thicker tumours
• Irregular diffuse pigmentation - pigmented blotches, the colour is brown with variable shades from tan to black
• Features found in other melanoma e.g. irregulalry distributed dots + globules, abnormal vascular patterns, signs of regression

	Figure 1 - Benign melanocytic naevus of the palm  (copied with kind permission from Dermatoweb)
	Figure 2 – Benign melanocytic naevus  (copied with kind permission from the International Dermoscopy Society)
	Figure 3 – Dermoscopic appearance of figure 2, parallel furrow patten Parallel furrow pattern (black arrow) (copied with kind permission from the International Dermoscopy Society)
	Figure 4 – Dermoscopic appearance of a benign melanocytic naevus, lattice-like pattern Dermsocopy reveals a lattice-like pattern (red arrow). The longitudinal pigmentation is still in the furrows (black arrow). The openings of the eccrine ducts are unaffected (purple arrows) (copied with kind permission from the International Dermoscopy Society)
	Figure 5 – Dermoscopic appearance of a benign melanocytic naevus, fibrillar pattern  (copied with kind permission from the International Dermoscopy Society)
	Figure 6 – Acral-lentiginous melanoma (copied with kind permission from Dermatoweb)
	Figure 7 – Melanoma Dermsocopy reveals a parallel furrow pattern (balck arrow) (copied with kind permission from the International Dermoscopy Society)
	Figure 8 – Subungual melanoma The lack of proximal sparing is cause for concern
	Figure 9 – Melanoma Subungual melanoma showing destruction of the nail
	Figure 10 – Talon noir This was referred by the podiatrist. Talon noir are harmless and result from trauma
	Figure 11 – Dermoscopic appearance of figure 10 The pattern is not too dissimilar from that found in the parallel ridge pattern of melanoma, although red globules of blood can be readily identified
	Figure 12 - Figure 10 after pairing down The superficial keratin was paired down - this confirmed the benign nature of the problem
	Figure 13 - Dermoscopic appearance of figure 12 No evidence of a melanocytic lesion. Please refer to the chapter on talon noir for further information

Diagnosis: Amelanotic melanoma

Key diagnostic features:

• Mainly present as smooth erythematous to pink plaques/nodules
• Lesions tend to grow over a number of months, but can grow more rapidly
• Some lesions may demonstrate small amounts of pigment in the lesion and/or adjacent skin
• With time lesions may become eroded
• Lesions can bleed but less so compared to pyogenic granuloma

	Figure 1 - Amelanotic melanoma left upper arm This was a new lesion in a patient with red hair. It was an 'ugly duckling' and looked different to her other moles
	Figure 2 - Dermoscopic appearance of figure 1 A polymorphous vascular pattern with dots (black arrow) and linear irregular vessels (blue arrows). Pigment globules are subtle (purple arrows) but show variation in size and are unevenly distributed
	Figure 3 – Amelanotic melanoma of heel
	Figure 4 - Amelanotic melanoma left heel The lesion had grown over a period of two years
	Figure 5 - Dermoscopic appearance of figure 4 Although the appearance was generally featureless, the presence of groups of globules at the periphery (black arrows) was suspicous of a hypomelanotic tumour Histology confirmed the diagnosis, the Breslow thickness was 2.3 mm
	Figure 6 – Amelanotic melanoma
	Figure 7 – Amelanotoic melanoma over lateral surface of the elbow The lesion grew to this size over a period of 6 months. It was initially diagnosed by the histopathologist as an atypical fibroxanthoma. However this did not fit with the clinical appearance and a review of the histopathology showed subtle features of a melanoma
	Figure 8 – Dermoscopic view of figure 7 This hypomelanotic lesion is relatively featureless - one must be wary of such dermoscopic findings. The milky red vascular appearance on the right hand side of the lesion also gave cause for concern. The curvy red lines (black arrows) are probably artefact, representing synthetic fibers from an article of clothing

Diagnosis: Metastatic melanoma

Can present in several ways:

• Local skin metastases
• Distant skin metastases
• Lymphadenopathy
• Internal organ metastases

On some occasions it is not possible to identify where the original primary melanoma was situated

	Figure 1 - Distant skin metastases
	Figure 2 - Local skin metastases The primary lesion had just be excised (to the right)