Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft-tissue neoplasm with a deceptively benign histological appearance and low-grade malignant potential which is often mistaken for other reactive or benign lesions. It most frequently harbors balanced t(7;16) translocation, and leads to the fusion of the FUS and CREB3L2 genes which can be detected by cytogenetic methods. Young adults are most commonly affected and it typically arises in the deep proximal extremities or trunk with frequent recurrences. It may metastasize to the lungs several years later. Paravertebral LGFMS is exceedingly rare and only few cases have been published in the literature. In those cases the novel immunohistochemical markers and cytogenetic studies were not performed and morphological mimickers could not be confidently excluded.We present a rare case of paravertebral LGFMS from a 54-years-old male patient, which previously was misdiagnosed as a neurofibroma with subsequent tumor recurrence. The concrete diagnosis was established by using MUC4 immunohistochemical stain and fluorescent in situ hybridization (FISH), which showed diffuse membranous positivity and supernumerary ring chromosome with unbalanced FUS gene rearrangement, respectively. The latter finding is also rare and may cause diagnostic dilemma if one is not aware of such uncommon, but well-documented phenomenon. Differential diagnosis with other low-grade spindle cell tumors will also be discussed along with the literature review.
Keywords: FUS; Low-grade fibromyxoid sarcoma; MUC4; supernumerary ring chromosome; t(7;16).
© 2016 by the Association of Clinical Scientists, Inc.