Histological evolution of lentiginous melanoma

I doubt that this variant exists. These are all melanoma in situ. It appears that some lesions can remain in this phase for many years but the nature of the lesion is the same. They do point out that significant solar elastosis was not associated with these lesions. I am sure Weedon and Kossard would report these are lentiginous dysplastic nevus of the elderly but these cases were a bit young for that designation!
Histological evolution of lentiginous melanoma: a report of five new cases
Authors: Davis, Tracy1; Zembowicz, Artur

Source: Journal of Cutaneous Pathology, Volume 34, Number 4, April 2007, pp. 296-300(5)

Abstract:

Background: 

The term lentiginous melanoma was recently used for atypical melanocytic proliferations sharing some histological features with lentigo maligna and associated with a protracted in situ stage before invasion. Lentiginous melanoma was characterized by predominantly single-cell lentiginous growth pattern with focal junctional nests and pagetoid spread, preservation of the dermoepidermal junction, limited cytological atypia, and lack of significant solar elastosis. We report five similar cases. Methods: 

Histological review of routine sections with clinicopathological correlation.
Results: 
Three patients were male and two were female. The age at presentation ranged from 24 to 66 years. All lesions arose on the truck or proximal extremities. All five cases fulfilled histological criteria proposed for lentiginous melanoma. None of the lesions showed significant solar elastosis. One lesion was followed clinically and histologically for 16 years without intervening treatment. It had three local recurrences before culminating in invasive melanoma.
Conclusions: 
Our observations support recent efforts to distinguish lentiginous melanoma as a distinct clinicopathological entity. Lentiginous melanoma can remain in situ for a long time before invasion and may be considered an analogue of lentigo maligna occurring on non-severely sun-damaged skin. Familiarity with the histological features of this variant is important for its early recognition and treatment.