Primary Dermal Melanoma
David Cassarino, MD, PhD
Key Facts
Terminology
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Primary cutaneous melanoma arising in dermis or subcutis, mimicking metastatic melanoma
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By definition, lacks any evidence of epidermal involvement, ulceration, or regression
Clinical Issues
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Often clinically suspected to be a cyst or epithelial tumor
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Complete and wider excision necessary
Microscopic Pathology
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Nodular, well-circumscribed, dermal &/or subcutaneous-based
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Composed of highly atypical melanocytes
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By definition, no overlying epidermal involvement, ulceration, or evidence of regression can be present
Top Differential Diagnoses
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Metastatic melanoma
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Primary nodular melanoma
Low magnification of a PDM shows a well-circumscribed, dermal-based nodule, mimicking metastatic melanoma. Note the grenz zone  separating the tumor from the overlying epidermis. |
High magnification of PDM typically shows marked cytologic atypia and multiple mitotic figures  . |
TERMINOLOGY
Abbreviations
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Primary dermal melanoma (PDM)
Synonyms
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Dermal &/or subcutaneous melanoma
Definitions
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Primary melanoma arising in dermis or subcutis, typically mimicking metastatic melanoma (MM)
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Clinically, lack of prior or concurrent melanoma by history and imaging studies
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