Skin-Melanocytic Tumors - Superficial spreading melanoma

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Skin-Melanocytic Tumors

Last major update: November 2008 - next update November 2009

Revised: 22 September 2009

Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.

Definition

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● Traditionally considered the most common type of melanoma (50-75%), but lentigo maligna may be more common in patients with extensive sun exposure (J Am Acad Dermatol 2008;58:1013)

● Recently diagnosed tumors are thinner with less ulceration than in the past (Cancer 2008 Nov 5 [Epub ahead of print])

Epidemiology

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● Usually affects light skinned individuals, young adults to elderly, often trunk and extremities

Case reports

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● 77 year old man with tumor in vertical growth phase with microscopic satellite nodule (Archives 2003;127:e365)

Risk factors

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● Extensive sun exposure during childhood, family history of melanoma, large numbers of benign nevi, dysplastic nevi

● Recommended to evaluate vertical growth phase as prognostic factor for thin (< 0.76 mm) tumors (AJSP 2003;27:717)

Clinical description

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● Variegated, black, brown, tan, blue, pink or white

● Slightly elevated, flat and irregular margins, often with an indentation or notch

● May have white areas of tumor regression or nodular areas of deep dermal invasion

Clinical images

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Irregular black tumor with Various images

elevation in periumbilical area

Dermoscopy

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● Multi-component pattern, asymmetry and multiple colors

● Also atypical reticular pattern (irregular holes and thick lines) with a sharp demarcation, blue-white veil, irregular linear vessels, central ulceration, irregularly distributed dots

Dermoscopy images

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Various images Reticular pattern with dark Homogeneous area,

broadened network irregular dots and

globules and irregular

branched streaks.

Micro description

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● Classified based on radial growth component (has nothing to do with level of dermal invasion)

● Noninvasive areas have asymmetry and poor circumscription, irregular acanthosis, irregular lentiginous and nested proliferation, uniform atypical melanocytes with nests and pagetoid cells

● Also transdermal migration, nuclear pleomorphism, dusty pigmentation, apoptosis of individual melanocytes, pigmented parakeratosis

● Invasive component generally of epithelioid subtype

Micro images

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Superficial spreading melanoma Clark level III

and satellite nodule

S100A6 staining (negative) Beta catenin expression in primary

but not metastasis

Molecular / cytogenetics

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● Exon 15 BRAF mutations in 29% (J Invest Dermatol 2005;125:575)

End of Skin-Melanocytic Tumors > Superficial spreading melanoma

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