Melanoma, Lentigo Maligna Type

 May be difficult to identify, especially if desmoplastic type or heavily inflamed





image
Papular Growth in Pigmented Patch
The marked area image, prior to biopsy, shows a papular growth in an ill-defined pigmented patch. This raises concern for a microinvasive melanoma. (Courtesy J. Finch, MD.)


image
Darkly Pigmented Papule on Elderly Earlobe
The marked lesion is concerning for melanoma image. This lesion stands out among the many seborrheic keratoses image on the left face and neck. (Courtesy J. Finch, MD.)

image
Atypical Pigmented Lesion With Inflammatory Regression of LMM
This broad, atypical melanocytic proliferation displays fibrosis image and patchy, inflammatory infiltrate image, consistent with inflammatory regression. Even the solar elastosis image is interrupted in the area of fibrosis.

image
Microinvasive Nest of LMM
Above the lentiginous atypical, melanocytic proliferation image, there is a prominent invasive nest image in the papillary dermis. Note the fibrosis (interrupted solar elastosis) image and inflammation image.


TERMINOLOGY


Abbreviations




• Lentigo maligna melanoma (LMM)


Synonyms




• Invasive melanoma, lentigo maligna type

• Hutchinson freckle (clinical term, which typically refers to melanoma in situ, lentigo maligna type)


Definitions




• Indolent melanoma subtype that evolves slowly and usually presents on head and neck (sun-exposed regions) in older patients


CLINICAL ISSUES


Epidemiology




• Age
image Older patients, typically > 60 years old


Site




• Usually on head and neck (sun-exposed regions)


Presentation




• Broad patch with nodule, may grow 5-10 cm or larger

• Variegated colors

• Irregular borders


Natural History




• Slowly evolving, indolent but invasive type melanoma


Treatment




• Surgical approaches
image Complete excision; margins depend on depth of invasion

image Mohs surgery if poorly defined margins; recurrence rates of < 1%

• Drugs
image Imiquimod cream is controversial but has shown promise for subset of patients
– Long-term follow-up and several posttreatment biopsies are encouraged, even with lack of clinical recurrence


Prognosis




• Surgical margins of at least 5 mm give cure rates of 90-95%


MICROSCOPIC


Histologic Features




• Severely atypical compound melanocytic proliferation with junctional lentiginous component (typical of lentigo maligna)
image Confluence of melanocytes replacing basilar keratinocytes, often forming cleft

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Melanoma, Lentigo Maligna Type

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