desmoplastic melanoma

Etiology: ultraviolet radiation is implicated. Epidemiology: 1) 4th to 9th decade, median age 56 2) more common in women 3) incidence: rare Pathology: 1) dermal fibroblastic component with minimal or absent melanocytic proliferation at the dermal-epidermal junction 2) nerve-centered with or without intra-epidermal melanocytic component 3) lesions may arise within lentigo maligna or acral lentiginous melanoma 4) may be atypical junctional melanocytic proliferation resembling lentigo maligna 5) S-100 positive spindle-shaped cells a) widely spaced, embedded in a collagen matrix b) may have non-membrane bound melanosomes 6) small aggregates of lymphocytes common at periphery 7) fibroblast-like tumor cells around or within endoneurium of small nerves Clinical manifestations: 1) variegated lentiginous macules, may have have blue-gray nodules 2) may appear as a dermal nodule without epidermal involvement 3) tumors commonly lack melanin or pigmentation 4) tumors may be gray to blue when melanin is principally within malignant dermal melanocytes 5) borders are irregular 6) may be large in size, thickness often > 2 mm 7) 85% on head & neck, majority on face, rarely on trunk 8) generally asymptomatic 9) other manifestations of sun-damaged skin a) telangiectasia b) marked freckling c) atrophy & solar keratosis Differential diagnosis: 1) basal cell carcinoma 2) blue nevus 3) Spitz nevus 4) metastatic melanoma 5) lentigo maligna 6) lentigo maligna melanoma 7) pigmented malignant schwannoma 8) dermatofibroma 9) neurofibroma 10) scar Management: 1) diagnosis is often delayed because of bland clinical appearance 2) surgical excision - local recurrence 50%, generally within 3 years 3) metastases to local lymph nodes in up to 20% if cases

References

Color Atlas & Synopsis of Clinical Dermatology, Common & Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 196-97