Low-Grade Fibromyxoid Sarcoma Featuring an Unusual EWSR1-CREB3L2 Gene Fusion: Report of a Rare Case Arising in the Parotid Gland

Abstract

Low-grade fibromyxoid sarcoma (LGFMS), also known as Evan's tumor, is a fibroblastic tumor with a deceptively bland morphology but a high metastasizing potential and late recurrence. It presents clinically as a slowly growing mass in the deep soft tissue of extremities and trunk. Morphologically, it shows a biphasic pattern with alternating fibrous and myxoid areas, whorling growth pattern, hypocellularity, and bland fibroblasts with curvilinear or arcuate vessels in between. Collagen rosettes with central hyalinization is a helpful feature but not specific. MUC-4 is the most sensitive immunostain in LGFMS. The majority of cases harbor a gene fusion in FUS-CREB3L2. Herein, we present a 23-year-old female patient with a slow growing painless mass in the left parotid gland, which was later diagnosed as LGFMS. Involvement of the head and neck region by LGFMS is uncommonly encountered. To date, only two cases within the parotid gland have been described.

Gene partners of the EWSR1 fusion may represent molecularly distinct entities

“…While some RFP have been previously reported in the literature, many RFP had not been previously reported ( Table S2). The RFPs identified included additional members of the ETS ( ETS1, ETV1, ETV4 [ 29 , 30 ], FEV [31] , [32] , [33] ) and CREB ( CREB3L2 [ 34 , 35 ], CREB3L3 [ 36 , 37 ], CREB3L4 ) TF families ( Table 2 ). The remaining RFPs were classified as other transcription factors (Other (TF) – Rare; n = 53) and non-transcription factors (Other (non-TF) – Rare; n = 49).…”