Is it possible to catch a nodular melanoma "in situ"?

Melanoma: (NM) is the most aggressive form of melanoma. It tends to grow more rapidly in thickness than in diameter. Instead of arising from a pre-existing mole, it may appear in a spot where a lesion did not previously exist . Since NM tends to grow in depth more quickly than it does in width, and can occur in a place that did not have a previous lesion, the prognosis is often poor in situ difficult diagn

Then is not called: as nodular melanoma , it is serious condition , how small it is when diagnosed already penetrated basal layer of skin causing early metastasis and unlikely possibility