Primary Dermal Melanoma
David Cassarino, MD, PhD
Key Facts
Terminology
Primary cutaneous melanoma arising in dermis or subcutis, mimicking metastatic melanoma
By definition, lacks any evidence of epidermal involvement, ulceration, or regression
Clinical Issues
Often clinically suspected to be a cyst or epithelial tumor
Complete and wider excision necessary
Microscopic Pathology
Nodular, well-circumscribed, dermal &/or subcutaneous-based
Composed of highly atypical melanocytes
By definition, no overlying epidermal involvement, ulceration, or evidence of regression can be present
Top Differential Diagnoses
Metastatic melanoma
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
Primary dermal melanoma (PDM)
Synonyms
Dermal &/or subcutaneous melanoma
Definitions
Primary melanoma arising in dermis or subcutis, typically mimicking metastatic melanoma (MM)
Clinically, lack of prior or concurrent melanoma by history and imaging studies
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