Pathology

1. Consist of loose nets of melanocytes in the basal cell layer which invade the epidermis (leading to destruction and ulceration)
2. Penetrate deeper into dermis and subcutaneous fat
3. Prognostic indicators
   • Clarke's levels
   • Breslow thickness
   • Known poor prognostic indicators: increasing age, male, melanomas of trunk, ulceration, depigmentation (amelanotic melanomas), aneuploidy and high mitotic index 

Approach

• Adequate exposure
• Examine as for any lump

1. Inspect
   • Most commonly found on legs of young women and trunk of middle-aged men
   • Location and characteristics depend on type
   • Commonest cancer of young adults agend between 20 and 29
   • Commoner in women than men
   • Rare sites - brain (substantia nigra contains melanin), eye (retina)
     

     Type		Incidence	Features
     Superficial spreading		Most common - 70%	Occurs legs of women, backs of men Red, white, blue in colour Irregular edge Usually palpable but thin
     Nodular		15 - 30%	Occurs most often on the trunk Polypoid in shape and is raised Smooth surface Irregular edge Frequently ulcerated
     Lentigo maligna			Arises in a lentigo maligna (Hutchinsons' melanotic freckle) Occurs most often on the face or dorsum of hands and forearm Underlying lesion is flat and brown-to-black in colour with an irregular outline Malignant area in the lesion is usually thicker, and darker in colour
     Acral lentiginous		Least common	Occurs on hairless skin (subungal area, palms of hands and oles) More common in Oriental and Black races Irregular area of brown or black pigmentation
     Amelanotic

Completion

1. Examine draining lymph nodes
2. Ask patient about symptoms from the lesion that may indicate malignancy
   • Loss of normal surface markins around the lesion
   • Ulceration
   • Evidence of bleeding
   • Marked variation in colour
   • Presence ofa halo of brown pigment in the skin around the lesion
   • Presence of satellite nodules of tumour around the lesion
3. Ask about predisposing risk factors
   • Congenital
     1. Xeroderma pigmentosum
     2. Dysplastic naevus syndrome (aka B-K mole or FAMM syndrome) - risk developing malignant melanoma = 100% if two family members are affected
     3. Large congenital naevi
     4. Family history in first-degree relative (increased risk by 1.5)
   • Acquired
     1. Sunlight: UV light, especially fair skinned people
     2. Pre-existing skin lesions - lentigo maligna, more than 20 benign pigmented naevia
     3. Previous melanoma (increases risk 3.5 times)

Differentials

1. Benign skin lesions
   • Moles - increased numbers of melanocytes producing too much melanin (aka pigmented naevus)
   • Freckles - normal numbers of melanocytes but each producing too much melanin
   • Lentigo - increased numbers of melanocytes producing normal amounts of melanin
   • Pigmented seborrhoeic keratoses
   • Dermatofibromas
   • Thrombosed haemangiomas
2. Malignant skin lesions
   • Pigmented basal cell carcinoma

Staging

1. Clarke's Levels

   	Clarke's Levels	Extent of tumour	5-year survival
   	I	Epidermis	98%
   	II	Invades papillary dermis	96%
   	III	Fills papillary dermis	94%
   	IV	Invades reticular dermis	78%
   	V	Subcutaneous tissue invasion	44%

2. Breslow thickness
   • Better prognostic indicator because reticular dermis is not uniformly thick in different parts of the body

3. Breslow thickness	10-year survival
   < 0.76mm	92%
   < 3mm	50%
   < 4mm	30%
   Lymph node involvement	<40% (8 year survival)

Treatment options

1. Prevention
   • Avoid causative factors
   • Public education
   • Suncream
2. Surgical excision
   • Main lesion
     1. < 0.76mm - excisewith 1cm margin
     2. 0.76 - 1.0mm - excise with 2cm margin
     3. > 1mm - excise with 3cm margin
     4. Excision should be down to fascia
   • Nodal spread
     1. If clinical suspicion of nodal metastatis, lymph node biopsy / FNAC
     2. If palpable lymph nodes, therapeutic block dissection
3. Palliation
   • Intralesional BCG
   • Immunotherapy - vaccines to raise an anti-melanoma antibody response, monoclonal antibody therapy, cytokine interferon therapy