Conventional histology vs. three-dimensional histology in lentigo maligna melanoma

Conventional surgery for lentigo maligna melanoma (LMM) is based on normal histological evaluation. However, such evaluation leaves diagnostic gaps. In contrast, complete three-dimensional (3D) histology of excision margins permits accurate detection of continuously spreading tumour strands like those of LMM. These can be specifically excised in tumour-positive areas with smaller excision margins, and better cosmesis and function. To date there have been no controlled studies of micrographic surgery of LMM.

Clinical parameters and surgical strategies influencing the prognosis of patients with LMM were evaluated in a prospective study of melanoma patients in the Department of Dermatology of the University of Tübingen (1980-99).

The 292 LMMs comprised 7.4% of 3960 primary stage I and II melanomas treated during this period. One hundred and thirty-six patients in this group (46.6%) underwent surgery on the basis of 3D histology.

The geometric mean excision margins were significantly smaller in the 3D histology group (P < 0.0001). Patients with micrographic surgery had fewer recurrences. Multivariate analysis of clinical, histological and surgical variables was carried out, and tumour thickness and 3D histology proved to be independent, significant factors for the prognosis of recurrence-free survival (relative risk, RR 2.08, P < 0.0001 and RR 2.11, P = 0.0037, respectively). There were no melanoma-related deaths in the 3D histology group. All 16 melanoma-related deaths were observed among the 156 patients of the conventional histology group (10.3%).

Excision of LMM using 3D histology resulted in a twofold lower probability of recurrence and twofold smaller excision margins. 3D histology is a valuable diagnostic tool and can be used in the management of LMM because of the latter's pattern of continuous tumour spread.