Melanoma maligna

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A tumour arising from melanocytes of the basal layer of the epidermis

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3. MALIGNANT MELANOMA
• A tumour arising from melanocytes of the basal layer of the epidermis
• Less commonly – uveal tract (eye) and meningeal membranes

INCIDENCE
• Global incidence is rising relentlessly
• In NI, the incidence rate of melanoma is increasing faster than any other tumour • 1996 – 181 new cases of malignant melanoma • On average 28 deaths due to melanoma each year

RISK FACTORS FOR MELANOMA
• Large numbers of benign naevi
• Freckles • Clinically atypical naevi • Severe sunburn • Early years in a tropical climate • Family history of MM

PATIENT EDUCATION

FAMILY HISTORY
• The majority of MMs occur in a sporadic pattern
• 2-10% of patients presenting with MM give a positive family history • In part this may be due to the inheritance of specific MM susceptibility genes eg, CDKN2A on chromosome 9 • Other reasons for familial clustering are atypical naevi and sun exposure

NAEVI
• CONGENITAL NEVI – occur in 1% of newborns. Tend to be large. Increased risk of MM
• ACQUIRED MELANOCYTIC NAEVI – 30-50% of all MMs arise in pre-existing naevi. ↑nos of naevi=↑risk MM

• ATYPICAL NAEVI / SYNDROME –association between a familial occurrence of MM and an atypical naevus phenotype

SUNSCREENS
• Have been promoted as protective agents
• But this is not supported by epidemiological data • ? Causal role of sunscreen chemicals

• ? False sense of security in those at risk – spend longer out doors but don‟t reapply appropriately

AIDS IN CLINICAL DIAGNOSIS
GLASGOW SYSTEM
Major: • Change in size • Irregular pigment • Irregular outline Minor: • Diameter >6mm • Inflammation • Oozing/bleeding • Itch/altered sensation

AMERICAN „ABCDE‟ SYSTEM
• Asymmetry

• Border
• Colour • Diameter • Examination

TYPES OF MELANOMA

NODULAR
• Commoner in males
• Trunk is a common site

• Usually thick with a poor prognosis
• Black/brown nodule • Ulceration and bleeding are common

SUPERFICIAL SPREADING
• The most common type of MM in the white-skinned population – 70% of cases • Commonest sites – lower leg in females and back in males • In early stages may be small, then growth becomes irregular

ACRAL LENTIGINOUS MELANOMA
• In white-skinned population this accounts for 10% of MMs, but is the commonest MM in nonwhite-skinned nations
• Usually comprises a flat lentiginous area with an invasive nodular component

SUBUNGAL MELANOMA
• Rare
• Often diagnosed late – confusion with benign subungal naevus, paronychial infections, trauma

• Hutchinson‟s sign – spillage of pigment onto the surrounding nailfold

LENTIGO MALIGNA MELANOMA
• Occurs as a late development in a lentigo maligna • Mainly on the face in elderly patients • May be many years before an invasive nodule develops

AMELANOTIC MELANOMA
• Diagnosis is often missed clinically • The lack of pigmentation is due to the rapid growth of the tumour and the differentiation of the malignant melanocytes

METASTATIC MELANOMA

PROGNOSTIC VARIABLES
• The Breslow thickness is the single most important prognostic variable (distance in mm of the furthest tumour cell from the basal layer of the epidermis)
Breslow depth In situ <1mm 1-2mm 5 year survival 95-100% 95-100% 80-96%

2.1-4mm
>4mm

60-75%
50%

• Scalp lesions worse prognosis, then palms and soles, then trunk, then extremeties • Younger women appear to do better than either men at any stage or women over 50 • Ulceration of the tumour surface is a high risk factor

MANAGEMENT
• Surgical excision – 1-3cm margins depending on breslow depth
• Invasive primary MM on the digits can be treated by amputation • Need to investigate all MMs over 1mm for metastases – CXR, USS abd or CT chest, abd, pelvis, bloods – FBP, LFTs, LDH • New scanning modality in Belfast – PET scan – for high risk primaries or evaluating lymphadenopathy

FOLLOW UP
• No general agreement on time period
• Depends on tumour thickness • Thick tumours – 5-10 years • Need to examine the scar and check for lymphadenopathy, liver, spleen, and total body examination for other suspicious naevi

PLANTAR MALIGNANT MELANOMA
• Caucasians – 1-9%
• Asians – 29-46% • Afro-Carribean – 6070%

SUBUNGAL MELANOMA
TRAUMA

Dwyer PK et al British Journal of Dermatology 1993;128:115-120
• 51 white caucasian patients west of Scotland with plantar melanoma • 20 – sup spreading melanoma • 27 – acral lentiginous • 4 – nodular • Female:male – 3:2
Thickn 5 yr -ess surv foot 0-1.49 82%

5 yr surv leg 95%

1.53.49
>3.5

51%
0%

71%
46%

Franke W et al Melanoma Research 2000;10:571-576
Type Age of MM foot 63.3 Thickn • Prognosis for plantar melanoma poor -ess 2.55
• Poor survival can be improved by a significant reduction in the time period between the first observation of a plantar skin lesion and surgical treatment

Rest of 52.6 body

1.22

Walsh SM et al The Journal of Foot and Ankle Surgery 2003;42(4):193-198

• “…..that the clinician must maintain a high index of suspicion when a patient presents with a pigmented or atypical lesion on the foot.”

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