Skin Cancer Superficial Spreading Melanoma | Dermatology Education Skin Cancer Superficial Spreading Melanoma Video
November 27, 2021

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Skin Cancer Superficial Spreading Melanoma

Clinical Subtypes

Four major clinical subtypes of melanoma are recognized, defined by clinical appearance, progression, anatomic site, and histologic appearance.

Superficial spreading melanoma

Superficial spreading melanoma is the most common subtype, accounting for 70-80% of all melanomas. It is most common in middle age, from the fourth to fifth decade. Of melanomas arising in a pre-existing lesion, most are superficial spreading. Superficial spreading melanoma is slightly more common in females than males and usually affects Caucasians. Any cutaneous site may be involved but they are most often found on the upper back of both sexes and on the legs of women. Lesions tend to be greater than 6 mm in diameter, flat and asymmetric with varying colors. SSM begins in a nonspecific manner and then changes shape by radial spread and regression. Lesions tend to spread laterally within the skin over a few years, before nodules develop. The random migration of cells, along with the process of regression, results in lesions with an endless variety of shapes and sizes. The shape is bizarre if left untreated for years. The hallmark of SSM is the haphazard combination of many colors, but it may be uniformly brown or black. Colors may become more diverse as time proceeds. A dull red color is frequently observed, which may occupy a small area or may dominate the lesion. The precursor radial growth phase may last for months or for years.