Desmoplastic Melanoma

Desmoplastic Melanoma
Soheil Sam Dadras, MD, PhD
Olubukola Babalola
David Cassarino, MD, PhD
Key Facts
Terminology
  • Invasive melanoma that often resembles an inflamed scar
Clinical Issues
  • Firm skin-colored, tan or pink plaque or nodule
  • Presents in sun-damaged skin of elderly adults
Microscopic Pathology
  • Discrete dermal lymphoid aggregates admixed with abundant collagen
  • Severe solar elastosis
  • “Pure” and “combined” (more cellular) subtypes
  • Ill-defined spindle cell neoplasm with highly infiltrative pattern of growth
  • Overlying epidermis may show melanoma in situ (usually lentigo maligna type)
Ancillary Tests
  • Immunostains for S100 and SOX10 usually positive
Top Differential Diagnoses
  • Dermal scar
  • Desmoplastic nevus
  • Spindle cell squamous cell carcinoma (SCC)
    • Positive for HMWCKs, p63; S100(−)
  • Atypical fibroxanthoma (AFX)
    • S100(−); CD10/CD68/CD99(+)
  • Dermatofibroma: FXIIIa/CD10(+); S100(−)
  • Dermatofibrosarcoma protuberans: CD34(+); S100(−)
  • Neural tumors
    • S100/SOX10(+); CD34(+) (not in DM)
  • Leiomyosarcoma
    • Actin/desmin (+), S100(−)
DM may resemble an inflamed scar on low-power examination. However, aggregates of lymphoid cells image and prominent solar elastosis image are usually identified and are helpful findings.
High-magnification examination shows hyperchromatic-staining atypical spindle cells image surrounded by abundant collagen image bundles.
TERMINOLOGY
Abbreviations
  • Desmoplastic melanoma (DM)
Synonyms
  • Desmoplastic/neurotropic melanoma
Definitions
  • Form of invasive melanoma composed of spindle cells associated with dense stromal collagen, resembling a scar
CLINICAL ISSUES
Epidemiology
  • Age
    • Presents in sun-damaged skin of elderly adults
Presentation
  • Firm skin-colored, tan or pink plaque or nodule
  • Sometimes depressed
  • Often amelanotic
Treatment
  • Surgical approaches
    • It is important to resect DM with clear surgical margins as early as possible for successful clinical management
    • 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
Prognosis
  • Tumor thickness
  • Clark level (IV vs. V)
  • Histological subtype: “Pure” (longer disease-free survival) vs. “combined”
    • “Pure” subtype is defined as > 90% scar-like areas
    • “Combined” subtype is defined as densely cellular spindle cell collections without significant scar-like areas (> 10%)
  • Tumor mitotic rate
MICROSCOPIC PATHOLOGY
Histologic Features
  • Ill-defined spindle cell neoplasm with highly infiltrative pattern of growth
  • Overlying epidermis may show melanoma in situ (usually lentigo maligna type)
  • Stromal collagen on scanning magnification resembles a scar
  • Spindle cells are arranged in fascicles and merge with scar-like areas
  • Cellular density and cytologic atypia can vary based on histologic subtype
  • Discrete dermal lymphoid aggregates
  • Solar elastosis
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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Desmoplastic Melanoma

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