LAUSR

OBJECTIVES We aimed to test the hypothesis that in retroperitoneal dedifferentiated liposarcoma (DDLS) the presence of the dedifferentiated (DD) component at the resection margin is associated with adverse outcome. METHODS We retrospectively searched the archive for primary resections of retroperitoneal DDLS performed at our institution between 1990 and 2017. Slides were rereviewed for diagnosis, Fédération Nationale des Centres de Lutte Contre le Cancer grade, myogenic differentiation, and the presence of the well-differentiated (WD) or DD component at the resection margin. The medical records were reviewed for patient age, sex, tumor size, tumor focality, adjuvant/neoadjuvant therapy, local recurrence, distant metastases, local recurrence-free survival (LRFS), overall survival (OS), and follow-up duration. RESULTS The presence of the DD component at the resection margin was associated with worse LRFS compared with cases without the DD component at the margin (P = .002). However, OS was not significantly affected (P = .11). CONCLUSIONS LRFS is significantly shorter in cases with the DD component at the margin compared with cases without DD tumor at the margin, while there is no association with OS. We recommend reporting the presence or absence of DD tumor at the margin in retroperitoneal DDLS, as it adds meaningful prognostic information.