Lentigo maligna melanoma - Altmeyers Encyclopedia

Synonym(s)

lentiginous melanoma; lentigo maligna melanoma; Lentigo maligna melanoma; Malignant melanoma at the base of a melanosis circumscripta praecancerosa

Definition
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Malignant melanoma of elderly people in chronically sun-exposed skin areas. Origins from its precursor lesion, the lentigo maligna.

Localization
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Especially face, lateral neck parts, décolleté, lower legs, forearms.

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Clinical features
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Brown or brown-black, 0.2-5.0 cm in size (rarely > 5.0cm), usually bizarrely circumscribed, brown to brown-black, variably colored plaque (no spot: a spot is not palpable, a plaque is characterized by a papable raised appearance). Lentigo-maligna melanoma develops chronically insidiously, "almost unnoticed" at the base of a lentigo maligna that has usually existed for years.
As the melanoma persists, intralesional nodule formation may occur. This usually differs in consistency and color (black) from the surrounding area.

Further Diagnosis:

Reflected light microscopy: Irregular pigment network with pseudopodia and regressions. The surface texture is no longer preserved.
High-resolution sonography: see below. Melanoma, malignant.

Histology
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Mostly atrophic surface epithelium. Differently pronounced actinic elastosis. Noticeable are an initially linear basal compression and the later occurring nestlike aggregation of atypical pigmented melanocytes. Individual atypical melanocytes are found in higher epithelial layers. A dense linear colonization of the hair follicular epithelium is regularly found. In plaque-shaped or nodular areas the basement membrane is broken through by melanocyte nests, so that tumor aggregates of varying density can be found in the dermis.

Therapy
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Different guidelines apply to the surgical therapy of lentigo-maligna melanoma than for other malignant melanomas.
In this type of melanoma, the safety margin recommended for other malignant melanomas can often not be adhered to for cosmetic or general medical reasons in cases of advanced age, multimorbidity or problematic localisation (eyelid, nose, cheek), in tumours with a tumour thickness of Breslow > 1.0 mm.
The situational operative measure will have to be adapted to acceptable safety distances. In this context, a 3D histology with immunohistological edge control is mandatory in order to create an R0 situation with a reduced safety margin. The study situation justifies this procedure (no increased local recurrence, no reduced survival rate).

Progression/forecast
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Due to the late metastasis, the prognosis is more favourable than for other types of melanoma. 5-JWR=80%.

Literature
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Moehrle M et al (2006) Conventional histology vs three-dimensional histology in lentigo maligna melanoma. Br J Dermatol 154: 453-459.
AWMF(2013) Guidelines program; S3 guideline "Diagnosis, therapy and follow-up of melanoma: https://register.awmf.org/assets/guidelines/032-024OLl_S3_Melanoma-Diagnosis-Therapy-Follow-up_2020-08.pdf.