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Case 37: A black spot

A 40 year old woman presents with this black spot on her back. Her husband thought it looked nasty and wasn't sure if it had been there before.

1. What is the likely diagnosis and the differentials?

Benign naevus

Malignant melanoma, pigmented BCC, Spitz naevus, seborrhoeic keratosis

2. What features on examination would make you suspect malignant melanoma?

A - asymmetry of shape
B - border irregular and indistinct
C - colour variation within the lesion
D - diameter greater than 6mm
E - environment of the lesion, ie its appearance in relation to the patient's other pigmented lesions, presence of satellite nodules and regional nodes

3. How would you manage this lesion?

If a patient is concerned about a lesion there is little to justify not making a definite histologic diagnosis even if it appears benign. A lesion that can be excised and closed readily should be taken with a margin of 1-2 mm. If melanoma is discovered the site will require re-excision but with margins determined by the thickness of the melanoma. A benign lesion will not require re-excision. A large lesion in a cosmetically difficult area or where simple closure may not be possible should have a punch biopsy taken to determine further management.