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Most Spitz nevi can be reliably diagnosed, but a small subset has histologic features usually associated with aggressive malignant melanomas (MMs). Difficult to classify, these lesions have been assigned descriptive names, such as atypical Spitzoid melanocytic tumors (ASMTs). Investigators retrospectively compared disease courses in young patients: 11 with ASMT and positive sentinel lymph nodes (SLNs) and 5 with unequivocal metastatic MMs and positive SLNs.
Worrisome features that differentiated the ASMT lesions from classic Spitz nevi were minimal or no maturation, absent or few Kamino bodies, and mitotic figures at the base. More than half of lesions occurred on the extremities. The median thickness was 4.6 mm, and most involved the reticu…