Desmoplastic Melanoma

 HMWCKs(+), p63; S100(-)



• Atypical fibroxanthoma
image S100(-); CD10/CD68/CD99 (+)

• Dermatofibroma: FXIIIA/CD10 (+); S100(-)

• Dermatofibrosarcoma protuberans: CD34(+); S100(-)

• Neural tumors
image S100/SOX10 (+); CD34(+) (not in DM)

• Leiomyosarcoma
image Actin/desmin (+), S100(-)



image
Scar-Like Appearance in DM
Desmoplastic melanoma (DM) may resemble an inflamed scar on a low-power examination. However, aggregates of lymphoid cells image and prominent solar elastosis image are usually identified and are helpful findings.


image
Cytological Atypia in DM
Unlike a scar, DM under high-magnification examination shows hyperchromatic-staining atypical spindle cells image surrounded by abundant collagen image bundles.

image
Dermal Lymphoid Aggregates in DM
This punch biopsy shows hyperkeratosis overlying an expanded dermis, mimicking an inflamed scar. There are discrete lymphoid aggregates image throughout the dermis that should raise suspicion for DM.

image
SOX10 Immunohistochemistry in DM
The presence of scar-like dermis and multiple lymphoid aggregates should be followed up by SOX10 (or S100) immunohistochemistry to confirm DM as in this case. The nuclei of tumor cells are strongly positive.


TERMINOLOGY


Abbreviations




• Desmoplastic melanoma (DM)


Synonyms




• Desmoplastic/neurotropic melanoma


Definitions




• Form of invasive melanoma composed of spindle cells associated with dense stromal collagen
image Resembles scar


CLINICAL ISSUES


Epidemiology




• Age
image 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
image It is important to resect DMs with clear surgical margins

– Needs to be done as early as possible for successful clinical management

image There is increasing evidence that sentinel lymph node biopsy may not be indicated for “pure” variants

– This variant has low incidence of regional lymph node metastases


Prognosis




• Tumor thickness (Breslow depth)
• Clark level (IV vs. V)

• Histological subtype: Pure (longer disease-free survival) vs. combined

image Pure subtype is defined as > 90% scar-like areas

image Combined subtype is defined as densely cellular spindle cell collections

– Lacks significant scar-like areas (> 10%)

• Tumor mitotic rate


MICROSCOPIC


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 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


Cytologic Features




• Pure subtype shows
image Spindle cells with often deceptively mild cytological atypia

image Nuclear hyperchromasia

image Irregular nuclear contours

image Minimal nuclear pleomorphism

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Desmoplastic Melanoma
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