Metastatic Dedifferentiated Liposarcoma of the Mediastinum with Osteosarcomatous Differentiation: A Case Report

Rationale: Liposarcoma is a malignant tumor of adipocytic differentiation that rarely arises within the mediastinum. Most of the existing data available comes from scattered case reports and a few small series.

Patient Concerns: A 51-year-old man was admitted with cough and sputum accompanied by fever. X-ray and CT showed a bulky anterior mediastinal mass that was initially misdiagnosed as a teratoma. PET/CT demonstrated a lesion on that location showing a small area of moderately intense uptake. After surgical excision, histopathological examination via hematoxylin and eosin first revealed the diagnosis of malignant undifferentiated tumors. The results of immunohistochemical evaluations were as follows: P63 (scattered +), VIMENTIN (giant cell +), CD68 (KPI; giant cell +), SMA (-), and Ki-67 (Li: 50%). Molecular pathology: MDM2 gene status (+) with amplification.

Diagnoses: The final histopathological diagnosis was dedifferentiated liposarcoma with osteosarcomatous differentiation.

Interventions: The patient underwent left mediastinal tumor resection, left upper lobe wedge resection and postoperative chemotherapy.

Outcomes: Mediastinal recurrences and chest wall metastases occurred quickly before the second round of chemotherapy 2 months later. Four months after surgery, the patient died.

Lessons: This paper presents a case of dedifferentiated liposarcoma with osteosarcomatous differentiation in a rare location: the mediastinum. Correct diagnosis is of importance for appropriate choice of therapy. Clinicians should be aware of the presence of a dedifferentiated liposarcoma within a mass on the mediastinum and enhancing treatment and management strategies for affected patients.