Desmoplastic Melanoma
Soheil Sam Dadras, MD, PhD
Olubukola Babalola
David Cassarino, MD, PhD
Key Facts
Terminology
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Invasive melanoma that often resembles an inflamed scar
Clinical Issues
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Firm skin-colored, tan or pink plaque or nodule
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Presents in sun-damaged skin of elderly adults
Microscopic Pathology
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Discrete dermal lymphoid aggregates admixed with abundant collagen
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Severe solar elastosis
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“Pure” and “combined” (more cellular) subtypes
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Ill-defined spindle cell neoplasm with highly infiltrative pattern of growth
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Overlying epidermis may show melanoma in situ (usually lentigo maligna type)
Ancillary Tests
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Immunostains for S100 and SOX10 usually positive
Top Differential Diagnoses
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Dermal scar
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Desmoplastic nevus
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Spindle cell squamous cell carcinoma (SCC)
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Positive for HMWCKs, p63; S100(−)
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Atypical fibroxanthoma (AFX)
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S100(−); CD10/CD68/CD99(+)
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Dermatofibroma: FXIIIa/CD10(+); S100(−)
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Dermatofibrosarcoma protuberans: CD34(+); S100(−)
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Neural tumors
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S100/SOX10(+); CD34(+) (not in DM)
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Leiomyosarcoma
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Actin/desmin (+), S100(−)
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TERMINOLOGY
Abbreviations
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Desmoplastic melanoma (DM)
Synonyms
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Desmoplastic/neurotropic melanoma
Definitions
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Form of invasive melanoma composed of spindle cells associated with dense stromal collagen, resembling a scar
CLINICAL ISSUES
Epidemiology
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Age
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Presents in sun-damaged skin of elderly adults
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Presentation
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Firm skin-colored, tan or pink plaque or nodule
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Sometimes depressed
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Often amelanotic
Treatment
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Surgical approaches
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It is important to resect DM with clear surgical margins as early as possible for successful clinical management
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There is increasing evidence that sentinel lymph node biopsy may not be indicated for “pure” variants of DM because of the low incidence of regional lymph node metastases
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Prognosis
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Tumor thickness
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Clark level (IV vs. V)
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Histological subtype: “Pure” (longer disease-free survival) vs. “combined”
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“Pure” subtype is defined as > 90% scar-like areas
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“Combined” subtype is defined as densely cellular spindle cell collections without significant scar-like areas (> 10%)
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Tumor mitotic rate
MICROSCOPIC PATHOLOGY
Histologic Features
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Ill-defined spindle cell neoplasm with highly infiltrative pattern of growth
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Overlying epidermis may show melanoma in situ (usually lentigo maligna type)
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Stromal collagen on scanning magnification resembles a scar
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Spindle cells are arranged in fascicles and merge with scar-like areas
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Cellular density and cytologic atypia can vary based on histologic subtype
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Discrete dermal lymphoid aggregates
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Solar elastosis
Cytologic Features

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