Giant Primary Mediastinal Well-Differentiated Liposarcoma With Bilateral Thoracic Extension Causing Complete Left Lung Collapse

Primary mediastinal liposarcomas are exceedingly rare mesenchymal tumors that can grow to a massive size before becoming symptomatic, often leading to diagnostic and therapeutic challenges. We present the case of a 45-year-old male with a giant, well-differentiated liposarcoma occupying the entire left hemithorax, anterior mediastinum and extending into the contralateral hemithorax, causing complete collapse of the left lung. The patient underwent a successful complete surgical resection via a single posterolateral thoracotomy, leading to an excellent postoperative outcome. This case highlights the importance of considering this rare entity in the differential diagnosis of large thoracic masses and underscores the feasibility and efficacy of complete surgical excision even for tumors of exceptional size. • Primary mediastinal liposarcomas are extremely rare and can reach massive sizes before causing symptoms. • Well-differentiated liposarcoma is the most common mediastinal subtype, frequently located in the anterior compartment. • CT and MRI are essential for assessing tumor extent, mediastinal involvement, and fatty composition; histopathology confirms the diagnosis. • Complete surgical resection via a single posterolateral thoracotomy is feasible even for giant tumors with contralateral extension. • Radical resection provides excellent outcomes, but long-term follow-up is required due to the risk of local recurrence.