Abstract
BACKGROUND: Liposarcoma is a malignant soft-tissue tumor that predominantly arises in the extremities and retroperitoneum. Primary mediastinum liposarcoma is extremely rare, accounting for 0.1–0.75% of all mediastinal tumors. Histopathologically, they are classified into four subtypes: well-differentiated, myxoid, pleomorphic, and dedifferentiated types, of which the myxoid type accounts for 30–40%. Here, we report a resected case of myxoid liposarcoma of the anterior mediastinum. CASE DESCRIPTION: A woman in her 50s was referred for an abnormal shadow on a chest X-ray at her medical checkup. Chest computed tomography showed a 40 mm round mass on the left side of the anterior mediastinum, with progressively darker staining and some areas of poor contrast. Magnetic resonance imaging showed T2-weighted high signal in the center with minimal diffusion limitation at the margins. Positron emission tomography showed a 18F-fluorodeoxyglucose avid tumor with maximum uptake value, 2.52. Tumor markers were within normal range. Preoperative diagnosis based on radiological findings was thymoma which was Masaoka I stage. Curative surgical resection was indicated and thoracoscopic total thymectomy was performed. Intraoperative findings showed invasion of the left phrenic nerve, so a combined resection was performed. Pathological examination showed short spindle-shaped atypical cells with dense, unordered proliferation and myxoid matrix deposition in the stroma. Involvement of the left phrenic nerve and diffuse infiltration of the surrounding fatty tissue were also observed. Genomic testing revealed the FUS-DDIT3/CHOP rearrangement. Taken together, the tumor was diagnosed as myxoid liposarcoma. CONCLUSIONS: Myxoid liposarcoma is of intermediate grade and has a relatively good prognosis compared with pleomorphic and dedifferentiated types. However, recurrence mortality rate is reported to be around 60%, and careful postoperative follow-up is necessary.