nodular melanoma

Introduction

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

Etiology

(risk factors)

• precursor lesions
  • congenital melanocytic nevus
  • dysplastic (Clark's) melanocytic nevus
• family history of melanoma
• light skin color with inability to tan
• excessive sun exposure, especially during preadolescence
• HCTZ (RR=1.2)

Epidemiology

• median age 40-50 years
• equal incidence in males & females
• occurs in all races
• 15-30% of melanomas in US
• 8 times more common than superficial-spreading melanoma in Japanese
• responsible for most melanoma deaths

Pathology

• arises in the dermal-epidermal junction
• extends vertically into the dermis
• epidermal growth limited to a small groups of tumor cells also invading the dermis
• surrounding epidermis is normal
• tumor may show large epithelioid cells, spindle cells, small malignant melanocytes or mixtures of the 3
• S100 & HMB-45 positive
• the tumor is in the vertical growth phase from the onset
• most aggressive form of cutaneous melanoma

Clinical manifestations

• uniformly elevated nodule or ulcerated thick plaque
• may be reddish-blue (purple) or blue-black; either uniform in color or mixed with brown or black
• may become polypoid & amelanocytic (pink) or tan
• early lesions are 1-3 cm, but may grow much larger if undetected initially
• oval or round with regular borders in contrast to other melanomas
  • most nodular melanomas are smooth, but others are eroded, portending poor prognosis
• distribution: upper back (most common), legs, anterior trunk (same as superficial spreading melanoma), on arms & legs in Japanese
• arises within 2-4 months to 2 years from normal-appearing skin or a melanocytic nevus

Laboratory

• excisional biopsy with narrow margins
• punch biopsy is acceptable when total excision is not feasible or impractical

Complications

• nodular melanomas
  • account for 14% of invasive melanomas
  • responsible for 43% of melanoma deaths

Differential diagnosis

• hemangioma: red or pink, can be blue or purple, slow growth
• pyogenic granuloma
• pigmented basal cell carcinoma
  • rolled, pearly, translucent borders, arborizing telangiectasias
  • dermoscopy distinguishes clinically
• keratoacanthoma
  • appears rapidily within 4-6 weeks as a round pink nodule with a central, keratin-filled crater
  • not black

Management

(same for superficial spreading & acral 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

• superficial spreading melanoma