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acral lentiginous melanoma

Cutaneous melanoma arising on the sole, palm, fingernail or toenail bed, or mucocutaneous skin of the mouth, genitalia or anus. Epidemiology: 1) occurs most often in Asians, sub-Saharan Africans & African Americans (50-70% of melanomas in these populations) 2) 7-9% of all melanomas, 2-8% in whites - most common skin cancer in people of skin color [5] 3) median age: 60-65 years 4) male:female ratio is 3:1 5) only melanoma subtype not associated with sun exposure Pathology: 1) intense lymphocytic infiltration at the dermal-epidermal junction 2) large melanocytes with prominent dendrites along the basal cell layer 3) melanocytes may form large nest extending into the dermis & along eccrine ducts 4) invasive malignant melanocytes often have a spindle shape giving the tumor a desmoplastic appearance Clinical manifestations: 1) slow growing tumor (2.5 year from appearance to diagnosis) 2) palm or sole (volar) type a) macular lesion in the radial growth phase with focal papules & nodules developing during the vertical growth phase b) color: marked variegation, blue, brown, black & depigmented pale areas c) 3-12 mm in size d) irregular borders, may be sharply or ill-defined e) distribution: soles, palms, fingers & toes 3) subungual type a) subungual macule beginning at the nail matrix, extending to involve the nail bed & nail plate b) papules, nodules & destruction of the nail plate may occur in the vertical growth phase c) color: dark brown to black pigmentation that may involve entire nail, often nodules & papules are unpigmented, may be amelanotic d) distribution: thumb or great toe e) periungual pigmentation (Hutchinson's sign) [3] 4) mucous membrane * images [4,6] Differential diagnosis: 1) plantar wart 2) subungual hematoma; subungual hemorrhage - pigmentation progresses distally as nail grows out creating a zone of clearing between the proximal nail fold & the pigmentation 3) fungal infection 4) pyoderma gangrenosum Management: 1) prognosis a) 5 year survival for volar type is 50% b) 5 year survival of subungual type is 80% 2) examine regional lymph nodes 3) surgical excisions a) melanoma in situ - excise with > 5mm margin b) thickness < 1 mm 1] excise with 10 mm margin 2] excise down to fascia or muscle if no underlying fascia 3] direct closure without graft often possible 4] node dissection only if palpable & suspscious for metastasis c) thickness 1-4 mm 1] excision with 20 mm margin 2] excise down to fascia or muscle if no underlying fasica 3] regional lymphadenectomy if sentinel node procedure is positive 4] lymph node dissection if regional lymph nodes are palpable d) thickness > 4 mm 1] excision with 30 mm margin 2] excise down to fascia or muscle if no underlying fascia 3] lymph node dissection if regional lymph nodes are palpable 4} amputation may be indicated 4) adjuvant chemotherapy a) interferon alpha-2b b) melphalan

General

cutaneous melanoma

References

  1. Color Atlas & Synopsis of Clinical Dermatology, Common & Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 204-206
  2. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 544
  3. Koh HK. Cutaneous melanoma. N Engl J Med 1991 Jul 18; 325:171 PMID: 1805813
  4. Warren MP, Harvey VM IMAGES IN CLINICAL MEDICINE. Acral Lentiginous Melanoma. N Engl J Med 2015; 373:1864. November 5, 2015 PMID: 26535515 http://www.nejm.org/doi/full/10.1056/NEJMicm1500906
  5. Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015
  6. DermNet NZ. Acral lentiginous melanoma. (images) http://www.dermnetnz.org/lesions/alm.html
  7. Goydos JS, Shoen SL. Acral Lentiginous Melanoma. Cancer Treat Res. 2016;167:321-9. Review. PMID: 26601870