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lentigo maligna

Macular intra-epidermal neoplasm. Precursor of lentigo maligna melanoma. Pathology: 1) early lesions confined to epidermis 2) thickening & invasion of underlying tissue indicates progression to lentigo maligna melanoma 3) insult to DNA of basilar layer melanocytes in sun-exposed skin 4) prolonged radial growth phase may precede progression to lentigo maligna melanoma 5) atypical cells are not distributing uniformly throught the lesion Epidemiology: - most common in elderly - lifetime risk: a) 4.7% 45 years of age b) 2.2% 65 years of age Clinical manifestations: 1) begins as uniformly pigmented light brown macule - evolves to pigmented macular lesions with variation in hues of brown & black 2) focal papular & nodular areas indicate invasion into the dermis & progression to lentigo maligna melanoma 3) 3 mm to 2 cm or larger in size 4) distribution: - single isolated lesion on sun-exposed surface (head & neck) 5) shape: irregular but sharply defined borders with inlets & peninsulas 6) enlarges gradually, over a period of years 7) other manifestations of sun-damaged skin a) telangiectasia b) marked freckling c) atrophy & solar keratosis d) basal cell carcinoma Laboratory: - shave biopsy - exception to do not shave a pigmented lesion Differential diagnosis: 1) lentigo maligna melanoma 2) solar lentigo Management: 1) check for regional lymphadenopathy 2) surgical excision a) margin of at least 1.0 cm beyond clinically visible lesion b) use of Wood's lamp may help define borders c) excision down to or including the fascia d) skin graft will be necessary e) dissection of regional lymph node only if clinically palpable f) neoadjuvant topical imiquimod, 5%, cream prior to conservatively staged excision may allow for negative histologic margins of 2 mm [4]

Related

lentigo maligna melanoma solar (senile) lentigo

General

lentigo; melanocytic macule

References

  1. Color Atlas & Synopsis of Clinical Dermatology, Common & Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 192-94
  2. Geriatrics Review Syllabus, American Geriatrics Society, 5th edition, 2002-2004
  3. Medical Knowledge Self Assessment Program (MKSAP) 16, 18 American College of Physicians, Philadelphia 2012, 2018.
  4. Donigan JM, Hyde MA, Goldgar DE et al Rate of Recurrence of Lentigo Maligna Treated With Off-Label Neoadjuvant Topical Imiquimod, 5%, Cream Prior to Conservatively Staged Excision. JAMA Dermatol. Published online May 30, 2018 PMID: 29847610 https://jamanetwork.com/journals/jamadermatology/fullarticle/2682576