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Skin-Melanocytic Tumors
Acral lentiginous melanoma
Last major update: November 2008 - next update November 2009
Revised: 3 November 2009
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.
Terminology
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● Acral: relating to or affecting the glabrous (non-hair bearing) or volar skin of the soles, palms and digits as well as the nail apparatus
Clinical
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● Usually palms and soles, subungual, mucocutaneous oral and nasal cavity, or anus
● More common in blacks and Asians; ~10% of melanomas in whites
● Often advanced at diagnosis because thickened, hyperkeratotic epidermis overlies and hides the primary lesion; often initially misdiagnosed (J Am Acad Dermatol 2003;48:183)
● Older age than other variants (66 vs. 52 years), associated with other malignancies, less often associated with sunburn
● May evolve slowly over years; mean 1 year to diagnosis in foot/ankle lesions (J Foot Ankle Res 2008;1:11)
● Rarely are multiple (Dermatol Surg 2007;33:1)
● Median disease free survival is 10 years (Br J Dermatol 2006;155:561)
Case reports
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● Initially treated as plantar wart (Dermatol Online J 2006;12(4):3, link)
Treatment and prognosis
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Poor prognostic factors:
● High mitotic rate, microsatellites (Br J Dermatol 2007;157:311)
Clinical description
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● In situ cases show longitudinal pigmented streak in nail plates, black pigmentation on proximal or lateral nail fold, irregular border or variegated pigmentation on sole or thumb (Am J Dermatopathol 2004;26:285)
● Invasive cases show densely pigmented macules with irregular borders
● Mean 3 mm, usually ulcerated (74%) (Cancer Causes Control 2008 Aug 29 [Epub ahead of print])
Clinical images
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Erosive and ulcerated foot Tumor of plantar Various images
lesion with pigment at periphery surface of foot
Dermoscopy
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● May have parallel ridge pattern (band-like pigmentation on ridges of skin markings is specific)
Micro images
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Contributed by Dr. Angel Fernandez-Flores, MD, PhD, Clinica Ponferrada, Spain:
Micro description
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● Confluent single-cell melanocytic proliferation
● Variable cytologic atpyia of melanocytes
● Prominent acanthosis of the epidermis with elongated rete ridges
● Pagetoid spread
● Proliferation of melanocytes downward along eccrine ducts
● Melanocytes may display prominent dendritic proceses
● Invasive component often composed of spindle cells, but epithelioid, small cells and pleomorphic cells are occasionally noted
● Intraepidermal lentiginous component is similar to lentigo maligna, but intraepidermal melanocytes are bizarre, epidermis is markedly hyperplastic, papillary dermis is widened and inflamed
● Early lesions may show proliferation of solitary melanocytes in crista profunda intermedia, the epidermal rete ridge underlying the ridge of the skin marking (Am J Dermatopathol 2006;28:21)
● Nail lesions show confluent stretches of solitary melanocytes, multinucleation, lichenoid inflammatory reaction and florid pagetoid spread (AJSP 2008;32:835)
Positive stains
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● S100 and HMB45 (Int J Dermatol 2003;42:123)
Differential Diagnoses
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● Acral lentiginous melanocytic nevi
End of Skin-Melanocytic Tumors > Acral lentiginous melanoma
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