Differentiating Melanoma In Situ from Severely Dysplastic Nevus with Anti-MART-1 Versus Anti-MiTF Immunohistochemistry: The Arkansas Experience
AJ Finn, BR Smoller, KM Hiatt. University of North Carolina Hospitals, Chapel Hill, NC; University of Arkansas for Medical Sciences, Little Rock, AR
Background: The distinction of melanoma in situ (MIS) from severely dysplastic nevus (SDN) is routinely complicated by coincident keratinocytic atypia and/or prominent interface change. Immunohistochemical stains for the melanoma antigen recognized by T cells (MART-1) can aid in diagnosis by highlighting lentiginous proliferation and pagetoid scatter not otherwise appreciated. However, recent reports of reactivity against nonmelanocytic cells with one widely used clone, as well as the appeal of a non-melanosome-associated, nuclear stain, have prompted a shift from anti-MART-1 to anti-microphthalmia-associated transcription factor (MiTF) antibody at our institution and others.
Design: In order to determine whether this shift was tantamount to a change in diagnostic criteria, we compared the number of diagnoses of MIS to that of SDN on the University Dermatopathology Service for the 11-month periods that directly preceded and followed the introduction of the anti-MiTF stain.
Results: We found the ratio of MIS to SDN diagnoses to be identical during both periods, including in the immunostained group, despite the sustained and near complete transition from anti-MART-1 to anti-MiTF. Interestingly, most cases of MIS and SDN were decided without the aid of an immunostain, though those that did involve one were more likely to be called MIS.
Diagnoses of MIS and SDN before and after adoption of anti-MiTF immunostain
Conclusions: This data suggests that the hematoxylin and eosin-stained slide remains the primary means of distinguishing MIS from SDN, with immunostains used mainly for confirmation in highly suspicious lesions with obscuring phenomena. These results and pattern of usage suggest that the increasingly common, subjective preference for anti-MiTF in the diagnosis of MIS should not be the basis of speculation regarding prior misdiagnosis of the same.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 43, Wednesday Morning