Superficial spreading melanoma

Superficial spreading melanoma is the most common malignant melanoma in both sexes (comprising 70% of the total) (1)

• it may arise de novo or in association with a pre-existing nevus (1)
• grows radially (lateral spread) before becoming invasive (2)
• average age of patients being 40 years old
• commonly seen on sun-exposed skin (specially in areas of intermittent sun exposure) (1)
• women tend to be affected more commonly on the back of the lower leg, whilst men are affected in the upper back (1)

Lesions are irregular brown, black or bluish black, frequently with some intermingled inflammation. A bizarre horseshoe-shaped or crescentic lesion may occur when the tumour shows central regression with concomitant peripheral extension. Active vertical invasion manifests clinically as raised and ulcerated nodules and is a poor prognostic sign. There is significant intra-epidermal lateral extension of melanocytes over at least three rete ridges beyond the later margin of dermal spread (1).

Reference:

• (1) Markovic SN et al. Malignant melanoma in the 21st century, part 1: epidemiology, risk factors, screening, prevention, and diagnosis. Mayo Clin Proc. 2007;82(3):364-80
• (2) Bristow IR et al. Clinical guidelines for the recognition of melanoma of the foot and nail unit. J Foot Ankle Res. 2010;3:25