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Skin-Melanocytic Tumors
Last major update: November 2008 - next update November 2009
Revised: 28 June 2009
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.
Terminology
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● Agminate nevi: means “clustered”; includes nevus spilus (flat mole), a discrete, hyperpigmented foci on a hyperpigmented macular background due to nests of nevus cells within superficial dermis associated with minimal basilar keratinocyte hyperpigmentation
● Neuronevus: congenital nevus with prominent neural features
● Giant congenital nevus: see below
Epidemiology
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● 1-2% of newborns (Dermatology 2007;214:227), 17% of Italian children ages 12-17 years, usually 6-15 mm
● Congenital usually refers to presence at birth, may also refer to clinical appearance or histologic pattern
Clinical
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● Usually larger than acquired nevi; may grow rapidly
● Often large, irregular in contour and pigmentation, hair bearing
● Associated with higher number of common melanocytic nevi and family history of melanoma, but not with sun exposure (Br J Dermatol 2008;159:433)
● May be associated with infantile hemangioma (J Am Acad Dermatol 2008;58:S16)
● Proliferative nodules in these nevi are often p53+ (67%) and c-kit+ (97%), but are usually benign and may regress (AJSP 2004;28:1017)
● Associated with nevus cells in lymph nodes (Am J Dermatopathol 2002;24:1)
● Overall risk of melanoma is 0.7% (Br J Dermatol 2006;155:1)
● Acral lesions resemble melanoma clinically
Case reports
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● With benign proliferative nodule (J Am Acad Dermatol 2008;59:518)
● With subsequent melanoma (Archives 2003;127:e343, J Plast Reconstr Aesthet Surg 2007 Dec 8 [Epub ahead of print])
● Halo congenital nevus in 56 year old woman with vitiligo (Australas J Dermatol 2008;49:229)
● With smooth muscle hamartoma (J Cutan Pathol 2008;35:83)
● Congenital panfollicular nevus (J Cutan Pathol 2007;34:14)
● Rapid severe repigmentation after curettage and dermabrasion (Br J Dermatol 2007;156:1251)
Treatment and prognosis
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● Early surgical removal, laser resurfacing in neonates (Br J Dermatol 2006;154:889)
Clinical images
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Various images
Dermoscopy description
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● Globules (83%), hypertrichosis (79%), and reticular networks (71%) (Arch Dermatol 2007;143:1007)
Dermoscopic images
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Haloed globules Target network and target globules
Reticular pattern and regular globules Globular pattern and patchy network
Micro description
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● Tends to involve reticular dermis, subcutis, skin adnexa, arrector pili muscles and nerves with single cell permeation of collagen
● Also neural differentiation with Wagner-Meissner-like corpuscles
● Frequent proliferative nodules
● Lesions of infants may have pagetoid melanocytic proliferation
Proliferative nodules:
● Dermal nodules of large epithelioid or spindled melanocytes that merge with surrounding nevus cells
● Often prominent nucleoli, cellular areas, focal hemorrhage and ulceration, but no necrosis, no destructive growth, minimal inflammation and 0-4 mitotic figures/10 HPF
● Lesions mature and regress over time
Micro images
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Fig 1,2: congenital nevus,
Fig 3: melanoma in axillary
node (inset: S100)
Molecular / cytogenetics
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● Lesions present at birth usually have NRAS but not BRAF mutations
● Lesions with congenital type histologic features but not present at birth more commonly have BRAF but not NRAS mutations (J Invest Dermatol 2007;127:179)
Video
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Differential Diagnoses
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● Glomus tumor
● Melanoma
Additional references
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Definition
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● May be defined as surface area of 144 cm2 or larger
● 2-42% risk of malignant transformation, with 6-14% lifetime risk of melanoma, often extracutaneous
● Dermatomal, “bathing suit” or “garment” configuration; may involve entire scalp, extremity, most of trunk or placenta
● May have satellite nevi, including within mucosal membranes
● Scalp lesions are often in thickened folds of skin resembling cerebrum, may involute in first 2 years of life (J Am Acad Dermatol 2008;58:508)
● Truncal nevi may develop symptomatic neurocutaneous melanosis (meningeal or cerebral melanosis), which is lethal in 1/3 (J Am Acad Dermatol 2006;54:767)
● May give rise to melanoma of skin or CNS or related neuroectodermal tumors (malignant peripheral nerve sheath tumor, cutaneous malignant melanotic neurocristic tumor, rhabdomyosarcoma, liposarcoma)
Terminology
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● Also called giant pigmented nevus or giant hairy nevus
Case reports
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● Newborn with neurocutaneous melanosis (J Neuroradiol 2007;34:272)
● Part of SCALP syndrome (J Am Acad Dermatol 2008;58:884)
● Neonatal patient with proliferative nodules (Clin Exp Dermatol 2008;33:125)
● Ulcerated and sclerotic lesion (Clin Exp Dermatol 2007;32:529)
● Desmoplastic giant congenital nevus with progressive depigmentation (J Am Acad Dermatol 2007;56:S10)
Treatment and prognosis
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● Possibly none for newborn scalp lesions
● Excision may require careful planning and several stages (Plast Reconstr Surg 2008;121:1674)
● Often split-thickness skin grafting (Ann Plast Surg 2008;60:283)
● Laser surgery if inoperable (Clin Exp Dermatol 2007;32:159)
Clinical images
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Newborn with giant Ulcerated nodule
hairy congenital nevus within the scalp
Fig 1: giant gyrus-like pigmented nevus of scalp before (A) and after (B) excision;
Fig 2: nevus cells in reticular dermis and subcutis; Fig 3: epithelium-like nevus
cells (A) and nevus cells containing melanin (B); Fig 4: some nevus cells are
surrounded by sebaceous glands
Micro description
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● Similar to congenital nevus
● Deeper nevus cells may be E-cadherin negative, contributing to their motility (J Dermatol Sci 2008;52:21)
Micro images
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Proliferation of melanocytes Melanocytes are uniform
along hair follicle in large ulcerated nodule
End of Skin-Melanocytic Tumors > Congenital nevus
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