Superficial Nodular Fasciitis With Atypical Presentations: Report of 3 Cases and Review of Recent Molecular Genetics

Abstract: Nodular fasciitis is a benign proliferation of fibroblasts/myofibroblasts that can be mistaken for an aggressive neoplasm because of its spectrum of appearances and anatomical locations, rapid growth, infiltrative growth pattern, and high mitotic rate. The presence of fusions involving USP6 gene in most cases provides a useful tool for diagnostic confirmation. Nodular fasciitis is often deep, in association with fascia, but less commonly, it arises superficially and can be biopsied by dermatologists. We present herein 3 such cases with confirmed USP6 rearrangement by fluorescence in situ hybridization (FISH) in which the diagnosis of nodular fasciitis was not initially obvious because of atypical morphologic and clinical features. These cases illustrate that in cutaneous myofibroblastic proliferations, nodular fasciitis should be given consideration even when encountered in unusual locations.