Sneddon

 
"Any change from the normal appearance is an indication for excision and histological examination. Malignancy should be suspected when a mole shows:
 
(a) Increased size.
(b) Increased depth of pigmentation and its extension into the surrounding skin.
(c) Crust formation or bleeding.
(d) An inflammatory areolar around the mole." (Fig. 6)
 
Sneddon IB, Church RE. Practical Dermatology. 3rd Edition. London: Edward Arnold (Publishers) Ltd., 1976:196.

View Figure  		Fig. 6  Our diagnosis and comment: Melanoma. The entire neoplasm pictured here, that is, the patch, plaque, papules, nodule, and tumor, represent a single pathologic process at different stages in the development of it, namely, melanoma. It is not a "melanoma arising in a senile freckle," but a melanoma de novo. A so-called senile freckle, known also, erroneously, as Hutchinson's melanotic freckle, precancerous circumscribed melanosis of Dubreuilh, and lentigo maligna actually is a melanoma in situ on skin, usually of the face, damaged badly by sunlight. The entire neoplasm shown here is a melanoma because it is asymmetrical, has a notched border, has an uneven surface, and is variegate in color.
 

Brief critique

 
What is said, conventionally, to be a mole transforming into melanoma actually is an evolving melanoma that arose de novo. Less than 20% of melanomas in Caucasians begin in asssociation with a pre-existing melanocytic nevus. A morphologist, looking for the first time, cannot appreciate an increase in size or an increase in depth of pigmentation; that information can be gleaned only by history or through photographs taken over time. By the time there is "crust formation or bleeding" and "an inflammatory areola around the mole," it is likely that the melanoma has metastasized.