In the early radial phase, the lesion is thin, and it can remain in this phase for months or years. This is the less threatening of the two phases, because once the melanoma enters into the vertical growth stage, the prognosis is worse. At this point, the cancer is a dangerous malignancy, because it has the ability to invade other tissues and metastasize. It arises very rapidly, is the most aggressive of all four types of melanoma, and, unfortunately, is also the second most widespread variety. Unlike the superficial spreading variant, which tends to spread outward, the nodular melanoma grows rapidly upward and inward.
NM usually develops in unblemished skin rather than in a nevus.
It is often in a fully invasive stage of growth when it is diagnosed. NM usually develops in middle-aged people. It feels very round, and the borders are smooth and regular. These lesions often are mistaken for blood vessel abnormalities because of their berry color and texture. This form of melanoma appears on palms, soles, or on nails.