Primary mediastinal dedifferentiated liposarcoma: Five case reports and a review.

Background: Liposarcoma has been subclassified histologically into well-differentiated, myxoid, pleomorphic, and dedifferentiated types. The dedifferentiated type generally shows poorer prognosis than the well-differentiated type. Because of its rarity, the clinicopathological features and clinical outcomes of primary mediastinal dedifferentiated liposarcoma remain unclear.

Methods: Five patients with primary mediastinal dedifferentiated liposarcoma were treated at Shinshu University Hospital between January 2012 and August 2017. We investigated the clinical characteristics, including age, gender, radiographic findings, pathological status, and clinical and treatment outcomes.

Results: Four of the five patients initially underwent radical surgical resection. One patient was disease-free after surgery, but the remaining three patients developed local recurrence in the mediastinum after surgical resection. Two of these patients underwent repeat surgical resection, resulting in long survival (60 and 40 months, respectively), while the other underwent proton beam therapy and showed no evidence of recurrence as of 17 months after treatment. The remaining patient was treated with chemotherapy using doxorubicin because of advanced inoperable disease, but failed to show a response and died within a month of the initiation of chemotherapy. Although the maximum standardized uptake values on fluorodeoxyglucose-computed tomography were relatively low, there was a slight positive relation between these values and the Ki-67-positive ratio in the tumor.

Conclusion: Aggressive treatment by surgical resection should be considered for mediastinal dedifferentiated liposarcoma, even in cases with local recurrence.