Melanoma In Situ, Lentigo Maligna Type
Soheil Sam Dadras, MD, PhD
Key Facts
Terminology
Melanoma in situ, lentigo maligna type (MIS-LMT)
Hutchinson melanotic freckle
Clinical Issues
Most common on face (in women) and on scalp, neck, and ears (in men)
Nonpalpable broad, slowly evolving pigmented patch
Strikingly variegated colors with irregular borders
Microscopic Pathology
Ill-defined lentiginous proliferation of atypical melanocytes along dermal-epidermal junction replacing basal keratinocytes
Epidermal atrophy accompanied by cytological atypia
Top Differential Diagnoses
Invasive lentigo maligna melanoma
Actinic (solar) melanocytic hyperplasia
Atypical (dysplastic) nevus
 Clinical photograph of a lentigo maligna type of melanoma in situ shows an irregularly shaped and unevenly pigmented  lesion on the scalp of an elderly patient. |
 Histologic examination of MIS-LMT shows a junctional melanocytic proliferation, which is composed of atypical, hyperchromatic-staining single cells, including several multinucleated tumor cells  . |
TERMINOLOGY
Abbreviations
Melanoma in situ, lentigo maligna type (MIS-LMT)
Synonyms
Hutchinson melanotic freckle
Precancerous melanosis of Dubreuilh
Definitions
Slowly evolving, indolent melanoma subtype that usually presents on head and neck (sun-exposed regions) in older patients
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Long-term exposure to ultraviolet irradiation
CLINICAL ISSUES
Epidemiology
Incidence
Very common subtype of melanoma in situ
Approximately 5% overall lifetime risk
Age
Older adults, usually > 72 years
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