desmoplastic melanoma

Etiology

ultraviolet radiation is implicated

Epidemiology

• 4th to 9th decade, median age 56
• more common in women
• incidence: rare

Pathology

• dermal fibroblastic component with minimal or absent melanocytic proliferation at the dermal-epidermal junction
• nerve-centered with or without intra-epidermal melanocytic component
• lesions may arise within lentigo maligna or acral lentiginous melanoma
• may be atypical junctional melanocytic proliferation resembling lentigo maligna
• S-100 positive spindle-shaped cells
  • widely spaced, embedded in a collagen matrix
  • may have non-membrane bound melanosomes
• small aggregates of lymphocytes common at periphery
• fibroblast-like tumor cells around or within endoneurium of small nerves

Clinical manifestations

• variegated lentiginous macules, may have have blue-gray nodules
• may appear as a dermal nodule without epidermal involvement
• tumors commonly lack melanin or pigmentation
• tumors may be gray to blue when melanin is principally within malignant dermal melanocytes
• borders are irregular
• may be large in size, thickness often > 2 mm
• 85% on head & neck, majority on face, rarely on trunk
• generally asymptomatic
• other manifestations of sun-damaged skin
  • telangiectasia
  • marked freckling
  • atrophy & solar keratosis

Differential diagnosis

• basal cell carcinoma
• blue nevus
• Spitz nevus
• metastatic melanoma
• lentigo maligna
• lentigo maligna melanoma
• pigmented malignant schwannoma
• dermatofibroma
• neurofibroma
• scar

Management

• diagnosis is often delayed because of bland clinical appearance
• surgical excision
  • local recurrence 50%, generally within 3 years
• metastases to local lymph nodes in up to 20% if cases

More general terms

• cutaneous melanoma

Additional terms

• desmoplasia