Black and Brown Skin Lesions

Black and brown skin lesions can be considered as melanocytic neoplasms. The important task is to exclude malignant melanoma that is increasing in incidence and is potentially fatal.¹
The commonest pigmented lesions include:

Common naevi

Most adults will have approximately 30 moles which they have been acquiring from infancy. New common moles rarely develop after age 40 years and any that do are suspicious.
Typical features of common naevi are:

• Symmetrical in area
• Even brown colouring (light or dark)
• Sharp margin
• <5 mm in diameter
• Profile varying from flat to pedunculated

Any one with >50 moles is at greatly increased risk of malignant melanoma, that may or may not arise from an existing mole. These patients need careful skin monitoring including baseline skin photography. Any lesion that starts to change colour, bleed, itch, be painful or increase in size needs excisional biopsy.

Atypical moles

Also known as dysplastic naevi, these are found in approx.1 in 12 Caucasians and do not usually become evident until puberty. These are easily mistaken for malignant melanoma because of their:

• Lack of symmetry
• Lack of sharp margin
• Size >6 mm
• Variation in colour within the lesion

Congenital naevi

These are found in approx. 1% of newborns and characteristically have:

• Variegated brown colour
• Sharp edge
• Rough surface
• Hair growing out of them

They are classified according to size:

• <1.5 cm - small
• 1.5 to 20 cm - medium
• >20 cm - large

Very large ones are known as giant naevi. Patients with large congenital naevi have a risk of up to 10% of developing MM often by age 10 years. These appear either within the lesion or as CNS melanoma.² Treatment is either excision or close monitoring. Laser treatment is also now available. ³

Malignant melanoma

Characterised by 'ABCDE' rule:

• Asymmetrical shape
• Irregular border
• Variegated colour
• Diameter changing
• Enlargement

However, not all these feature may be present and if MM cannot be excluded then excision biopsy is required.⁴

Blue naevus

Despite its name, this lesion is usually a shade of blue-black. It is also called the Tièche-Jadassohn naevus.⁵ These occur in children and adolescents as solid papules or nodule of 10 mm in diameter with a round or oval, irregular shape. Mostly found on the back of the hand or top of foot, also on head, lower back and buttocks. Newly occurring lesion may need excision biopsy to exclude nodular MM. ⁶

Spitz naevus

This is a dark brown, smooth, firm papule or nodule that rarely occurs after age 40 years. These grow rapidly on the head and neck. Require careful excision with 5mm border to avoid recurrence.⁷