The elusive BAP1 mutation in pediatric melanocytic tumors

Cutaneous BAP1-inactivated melanocytomas (BIM) are melanocytic proliferations defined histopathologically by an epithelioid, predominantly dermal melanocytic proliferation with loss of BAP1, and have been largely characterized in adult patients but less well-described in pediatric cohorts. BIM share overlapping histological features with those seen in Spitz nevi; however, unlike Spitz nevi, the majority of BIM carry both BAP1 and BRAF^V600E mutations. This study investigated the potential overlap of BIMs with pediatric Spitz nevi by performing immunohistochemical staining of BAP1 and BRAF^V600E on pediatric melanocytic tumors with banal Spitz and dermal features. None of the stained tumors in our study exhibited the concurrent BAP1 loss and BRAF^V600E positivity that are characteristic of adult BIM, suggesting that this is a low-frequency mutation among banal tumors in the pediatric population.