8745/3 Desmoplastic melanoma, malignant



Definitions

Skin
ICD-O-3 topography code: C44
ICD10: C43
           

Desmoplastic melanoma (DM) is a melanoma of the skin histologically characterized by a proliferation of atypical spindled melanocytes in the dermis on a background of abundant collagen fibres or fibrous stroma. The malignant cells often resemble fibroblasts and are usually non-pigmented. They infiltrate deeply into the reticular dermis and may involve deep fascia, especially pericranium. Vascular invasion is rare. Small islands of lymphocytes and plasma cells are typically found within and/or at the edge of the tumour.
At least 30% of cases display neurotropism; these tumours are termed desmoplastic neurotropic melanomas (DNM). Neurotropic foci, in which the spindle cells extend around nerves, may be found well beyond the main tumour. The majority of desmoplastic melanomas develop on sun-exposed sites, most commonly in the head and neck region, and usually manifest as indurated or nodular lesions. Ulceration is uncommon.
Almost 50% are amelanotic; these lesions are often mistaken for basal cell carcinoma, dermatofibroma or a scar. Pigmentation is usually due to an associated lentigo maligna or superficial spreading melanoma.
Desmoplastic melanomas account for 1-4% of melanomas. They arise predominantly in elderly patients and show a predilection for males (ratio 1.75:1). Treatment of choice is wide local excision; recurrence is common after incomplete or marginal (<10mm) excision or if neurotropism is present. Initial metastases may involve regional lymph nodes or distant sites1
 
LeBoit PE, Burg G, Weedon D, Sarasin A (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Skin Tumours
3rd Edition
IARC Press: Lyon 2005



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