Growth and Development of Primary Skin Melanomas: A Short Atlas

Melanomas develop initially as a flat phase without competence for metastasis called the radial growth phase. They then may evolve focally an elevated part, the vertical growth phase, with metastatic competence.

Generally, the radial growth phase is described by the A,B,C,D’s of melanoma:

A = asymmetry

B = border irregularity

C = color variability (brown, black, blue, gray, pink)

D = diameter of (often) greater than 1/4 inch

Radial growth phase melanomas, although invasive, have a cure rate that approaches 100% with surgery alone. Figures 1 and 2 are radial growth phase melanomas of the superficial spreading type, the most common form in white populations. This type is associated with excessive, intermittent sun exposure (especially in childhood and youth).

Figures 3 and 4 are radial growth phase melanomas of the lentigo maligna type. This type is associated with a lifetime of immoderate sun exposure and hence generally occurs in aged, sun damaged, maximally exposed skin.

Figures 5 and 6 are radial growth phase, acral-lentiginous melanomas. These occur in all races at a very low rate on palms, soles of the feet, and under the nails.

Figures 7, 8, and 9 are melanomas that have evolved focal areas of vertical phase. Overall, patients with vertical growth phase melanomas have a cure rate of 70%. Individual prognosis is dependent on such factors as tumor thickness, lymphocytic infiltration into the vertical growth phase, proportion of tumor cells in mitosis, ulceration, tumor location, and the patient’s sex.