PRAME-negativity in sclerosing nevi with pseudomelanomatous features supports classification as an indolent lesion

Some dysplastic nevi, termed sclerosing nevi with pseudomelanomatous features, may have florid fibroplasia associated with features that cause melanoma to be a prominent consideration in the differential diagnosis. PRAME (PReferentially expressed Antigen in MElanoma) immunohistochemistry (IHC) has been shown to be a useful marker in the distinction of melanoma and nevus. PRAME expression in such sclerosing nevi with pseudomelanomatous features has not been evaluated to our knowledge. Thirty-two sclerosing nevi with pseudomelanomatous features were stained with PRAME IHC, with positive labeling defined as staining of >75% of the cytomorphologically atypical lesional cells. All 32 cases had variable cytologic atypia, bridging of elongated rete, fibroplasia, and a vertically oriented trizonal appearance. Some cases (23/32) had centrally located flattening of the rete ridge pattern bilaterally flanked by fibroplasia associated with elongated rete. PRAME labeling was negative (