Hello,
We cannot judge just from the appearance of a lump whether it is a neoplasm or malignancy or not.
Melanoma has an irregular border,asymmetrical,uneven color and increasing in size. If you notice changes in the mole's color, height, size or shape, you should have a dermatologist evaluate it.
So it would be only after a biopsy that it can be confirmed whether the growth is a malignancy or not. Moreover from the biopsy, we can confirm the staging and prognosis of the growth.