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Most primary melanomas go through phases of growth—a radial growth
phase and a vertical growth phase—while staying confined to the outer skin
layer (epidermis) and inner skin layer (dermis). During the radial growth
phase, melanoma grows out into skin on the side but only slightly down into the
skin layers. Cancer cells stay in the epidermis, the area between the epidermis
and dermis, and the upper dermis. Primary melanomas rarely spread (metastasize)
to other sites in the body in this phase. Thin, radial-growth–phase primary
melanomas are easily cured by surgical removal (excision).
During the vertical growth phase, the cancer grows down into skin,
and a small raised bump (nodule) may develop on the surface of the melanoma.
Melanoma that has entered the vertical growth phase is more likely to spread to
other parts of the body and is more difficult to cure than is
Slingluff CL, et al. (2008). Cutaneous melanoma. In VT
DeVita et al., eds., DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology, 8th ed., vol. 2, pp. 1897–1951.
Philadelphia: Lippincott Williams and Wilkins.
October 12, 2012
Kathleen Romito, MD - Family Medicine & Amy McMichael, MD - Dermatology
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