Maize et al.

 
"The earliest lesions of most melanomas in situ, small macules clinically, appear microscopically as proliferations of solitary melanocytes at or slightly above the dermoepidermal junction, spaced at irregular intervals. The nuclei of melanocytes in these early neoplasms may or may not be cytologically atypical, but are almost always larger than those of the non-neoplastic basilar melanocytes. As lesions of melanoma in situ evolve, melanocytes can aggregate to form nests and spread to the upper spinous, granular, and cornified layers. Often, single neoplastic melanocytes will be visible beyond the last nest on either side of the lesion, and some of these cells may be situated above the basal layer. Melanoma in situ typically involves follicular infundibula and acrotrychia [sic] in a given lesion with melanocytes distributed in the same pattern as they are within the interadnexal epidermis." Maize JC et al. Cutaneous pathology. Philadelphia: Churchill Livingstone, 1998:689.
 

Brief Critique

 
Most of the criteria presented here were forged in conjunction with Ackerman, who, in 1987, together with Maize, did a book titled "Pigmented Lesions of the Skin."*
*Maize J, Ackerman AB. Pigmented lesions of the skin. Philadelphia: Lea & Febiger