Meara

 
"The lesion is usually deeply pigmented and in those arising from a pre-existing cellular naevus the first change may be an irregularity in pigmentation of the lesion. Pigment may then spread laterally from the naevus to produce an irregular blotchy halo of pigmentation. The lesion becomes thicker and may bleed readily.
 
On normal skin the lesion may appear as a pigmented nodule which rapidly ulcerates and invades the dermis. Sometimes the malignant cells invade laterally producing a macular pigmented lesion or a slightly raised plaque."
 
Meara RH. Epithelial and melanocytic tumours of the skin. In: Marks R, Samman PD, eds. Dermatology. New York: Appleton-Century-Crofts, 1977:102.
 

Brief critique

 
A macule of melanoma that develops de novo is not usually deeply pigmented and a macule that comes into being in association with a pre-existing melanocytic nevus evolves in the same manner as does a melanoma that arises de novo. There are no differences between them in clinical appearance, except for those in which the pre-existing nevus is still obvious, having not yet been overrun by the abnormal melanocytes of melanoma. By the time that a melanoma is sufficiently thick to "bleed readily," metastases from it in all likelihood have occurred. A melanoma, whether it arises de novo or in conjunction with a nevus, begins as a macule and not "as a pigmented nodule which rapidly ulcerates and invades the dermis."