Melanoma In Situ, Superficial Spreading Type
Soheil Sam Dadras, MD, PhD
Key Facts
Terminology
Melanoma in situ composed mostly of irregular nests spreading along dermal-epidermal junction
Clinical Issues
Most common variant of melanoma
Broad pigmented macule, variegated colors, irregular borders
Sites vary: Often back (in men), legs (in women)
Excellent prognosis
Microscopic Pathology
Spread of atypical single cells and nests along junction (radial growth phase)
Abundant pagetoid scatter of atypical melanocytes into spinous layer
Top Differential Diagnoses
Severely atypical (dysplastic) junctional nevus
Traumatized nevus or of special site
Reed (pigmented spindle cell) nevus
 Low magnification of a MIS-SST shows an atypical intraepidermal melanocytic proliferation in all layers of the epidermis and irregular nests of atypical cells along the dermal-epidermal junction  . |
 Higher power magnification reveals multifocal pagetoid scatter of atypical, epithelioid-shaped melanocytes throughout all layers of the epidermis  . |
TERMINOLOGY
Abbreviations
Melanoma in situ, superficial spreading (MIS-SST) type
Synonyms
Superficial spreading melanoma in situ
Definitions
Earliest stage of melanoma limited to epidermis, showing spread along dermoepidermal junction (radial growth phase)
CLINICAL ISSUES
Epidemiology
Incidence
Most common variant of melanoma
Age
Generally adults
Gender
Males and females, different site predilections
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