Primary Pulmonary Myxoid Sarcoma with <i>EWSR1::ATF1</i> Fusion: A Case Report

Abstract

Primary pulmonary myxoid sarcoma is a rare lung sarcoma, mostly involving the central lung and harboring the <i>EWSR1::CREB1</i> fusion. We report an exceptional case of primary pulmonary myxoid sarcoma arising in the peripheral lung and harboring an <i>EWSR1::ATF1</i> gene fusion. A 67-year-old man presented with a solid nodule in the right lower lobe, and wedge resection was performed. Microscopically, the tumor consisted of reticular proliferation of uniform mildly atypical spindle cells within abundant myxoid stroma. Immunohistochemically, smooth muscle actin was positive but desmin was negative. Fluorescence in situ hybridization confirmed <i>EWSR1</i> and <i>ATF1</i> gene rearrangements. No recurrence was seen for 12 months. Pathological findings and gene rearrangements are important for the diagnosis of primary pulmonary myxoid sarcoma. Complete resection and careful observation are required.