superficial spreading melanoma

Introduction

Most common of tumors that arise in melanocytes of individuals with white skin.

Etiology

(risk factor)

• presence of precursor lesions
  • congenital melanocytic nevus
  • dysplastic (Clark's) melanocytic nevus
• family history of melanoma
• light-skinned individual with inability to tan
• excessive sun exposure, especially during preadolescence

Epidemiology

• adults 30-50 years of age
• slightly higher incidence in females
• white race, rare in brown- & black-skinned individuals
• 70% of melanomas in white persons
• 10% arise in high-risk families
• 90% of cases are sporadic

Pathology

• large, atypical melanocytes throughout epidermis in multiple layers, occurring single or in nests
• melanocytes often have regularly dispersed fine particle of melanin
• spindle cells & small malignant melanocytes may be present
• intra-epidermal radial growth of pigmented cells (carcinoma in-situ)
• vertical growth of malignant cells which invade the dermis
  • occurs over months to years
  • potential for metastases

Clinical manifestations

• flattened papule, becoming a uniformly elevated plaque with irregular border, expanding in diameter, then developing one or more nodules
• dark-brown to black with admixture of pink, gray, blue-gray, violaceous hues - marked variegation & haphazard pattern
• white areas indicate regressed areas
• size 5 mm - 2.5 cm
• asymmetrical lesions, irregular, sharply-defined borders
• isolated single lesions
• distribution: upper back (most common in men), legs (most common in women), anterior trunk, may occur in regions traditionally not exposed to sun
• 1/2 of melanoma in blacks (rare) develop on sole of foot
• moderately slow-growing lesion over a period of 1-2 years

Diagnostic criteria

ABCDE of diagnosis A: Asymmetry B: Border is irregular C: Color is mottled haphazard mixture of brown, black, gray, pink D: Diameter is large > 6 mm E: Enlargement and elevation of lesion

Laboratory

• excisional biopsy with narrow margins
• Wood's lamp may help define borders
• epiluminescence microscopy increases diagnostic accuracy
• punch biopsy when excisional biopsy not feasible/impractical

Management

(same for nodular & acral lentiginous melanoma):

• examine regional lymph nodes
• surgical excisions
  • melanoma in situ
    • excise with > 5mm margin
  • thickness < 1 mm
    • excise with 10 mm margin
    • excise down to fascia or muscle if no underlying fasica
    • direct closure without graft often possible
    • node dissection only if palpable & suspscious for metastasis
  • thickness 1-4 mm
    • excision with 20 mm margin
    • excise down to fascia or muscle if no underlying fasica
    • regional lymphadenectomy if sentinel node procedure is positive
    • lymph node dissection if regional lymph nodes are palpable
  • thickness > 4 mm
    • excision with 30 mm margin
    • excise down to fascia or muscle if no underlying fasica
    • lymph node dissection if regional lymph nodes are palpable
• adjuvant chemotherapy
  • interferon alpha-2b
  • melphalan

More general terms

• cutaneous melanoma

Additional terms

• sentinel lymph node procedure