Acral lentiginous melanoma in situ – low magnification
LEGEND
The nests are irregularly spaced. They have an irregular shape within the dermal papillae, and some are confluent.
Proliferation of melanocytic nests of variable sizes, poorly defined, and arranged asymmetrically
A lentiginous proliferation of melanocytes is observed at the periphery, beyond the clustering in nests.
Acral lentiginous melanoma in situ – high magnification
LEGEND
Pagetoid ascent can sometimes be observed in benign lesions, especially in the center of an acral nevus.
Presence of pagetoid ascent (i.e., melanocytes migrating upward to the stratum corneum) throughout the lesion, particularly at the periphery
Acral lentiginous melanoma in situ – high magnification
LEGEND
Mitoses may sometimes be observed.
Pleomorphism means the cells vary in size and shape.
The nests are composed of epithelioid and/or spindle cells with cytologic atypia (hyperchromasia, pleomorphism, prominent nucleolus)
Melanin granules
Acral lentiginous melanoma in situ
Melan-A positive. This allows better visualization of nest irregularity, pagetoid ascent, and the absence of dermal invasion.
