USP6 rearrangement in pediatric nodular fasciitis.

Nodular fasciitis (NF) is a myofibroblastic proliferation that is uncommonly present in pediatric patients. These benign neoplasms can masquerade as more insidious sarcomatous proliferations on both clinical exam and initial histopathologic review, often prompting undue concern in patients, parents, and providers. While immunohistochemical analysis of NF can be variable, adding to the diagnostic uncertainty, molecular analysis documenting ubiquitin-specific protease 6 (USP6) gene rearrangement can help confirm the diagnosis as an association between NF and USP6 overexpression was first identified 10 years ago in an analysis that found rearrangements of the involved locus in over 90% of studied samples. In this report, we review one case of NF located on the chin of a nine-year-old girl in which molecular testing was essential to secure the correct diagnosis, and provide a summary of documented cases of USP6 overexpression in transient pediatric neoplasms.