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Skin-Melanocytic Tumors
Last major update: November 2008 - next update November 2009
Revised: 26 October 2009
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.
Definition
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● Atypical melanocytes in basal layer, individually and in nests (theques), associated with sun damage
Terminology
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● Also called melanoma arising in Hutchinson’s freckle, actinic melanosis, melanoma on sun damaged skin, solar melanoma
Clinical
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● 5-15% of (invasive) melanoma; increasing prevalence, particularly among men age 65+ years (J Invest Dermatol 2005;125:685)
● Slow growing lesion of sun exposed skin of elderly whites, often cheek; partial regression is common
● Similar behavior to other melanoma subtypes when depth of invasion is considered, but unusual to die of disease
● Possible origin from progenitor stem cell (strongly CD133+ and CD34+) in outer root sheath of the mid-lower hair follicles (Dermatol Ther 2008;21 Suppl 1:S1)
● Note: lentigo maligna (a subtype of melanoma in situ), by definition, does NOT infiltrate into dermis, but lentigo maligna melanoma has at least single cell infiltration into papillary dermis
Case reports
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● Present (in retrospect) in 22 year old woman (Dermatology 2008;217:66)
● Collision tumors: - with basal cell carcinoma (Am J Dermatopathol 2005;27:319), with Merkel cell carcinoma (J Cutan Pathol 2008;35:203)
Treatment and prognosis
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● Excision with careful margin control (J Am Acad Dermatol 2008;58:142)
● Staged excision for peripheral margin control using permanent sections is required because frozen sections are unreliable (Plast Reconstr Surg 2007;120:1249)
● Possibly radiation (Surg Clin North Am 2003;83:323)
● Possibly imiquimod without (Ann Plast Surg 2008;61:419) or with surgery (Dermatol Surg 2008;34:147)
● Possibly cryotherapy
Clinical description
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● Flat, tan to black with irregular hyperpigmentation, > 2 cm
Clinical images
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Various images
Dermoscopy
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● Annular-granular pattern
● Asymmetric pigmented follicular openings
● Dark rhomboidal structures
● Homogeneous areas
Dermoscopy images
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Annular-granular pattern
Annular-granular pattern with slate-gray dots, Annular-granular structures, asymmetric
rhomboidal structures and homogeneous area follicular openings and rhomboidal structures
Asymmetrical pigmented follicular openings,
rhomboidal structures and some homogenous areas
Micro description
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● Contiguous growth of atypical melanocytes in basal layer, individually and in nests (theques)
● Cells may be spindled, pleomorphic and have cytoplasmic retraction
● Dermis shows solar elastosis
● Also epidermal atrophy, actinic damage, basilar keratinocyte hyperpigmentation
Micro images
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Atypical melanocytes involving epidermis and adnexal epithelium and infiltrating dermis
Contributed by Angel Fernandez-Flores, MD, PhD, Hospital El Bierzo and Clinica Ponferrada, Spain
Differential Diagnoses
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● Desmoplastic melanoma (may arise secondary to lentigo maligna)
Additional references
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End of Skin-Melanocytic Tumors > Lentigo maligna melanoma
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