Correlation of histological grade of dedifferentiation with clinical outcome in 55 patients with dedifferentiated liposarcomas.

In this study the histologic grade of dedifferentiated liposarcomas was correlated with outcome in surgically resected specimens in 55 patients over a 19-year period at the University of Pittsburgh Medical Center. The tumors were located in the retroperitoneum (N=35); the extremities and thigh (N=16), and the remainder involved the spermatic cord and head and neck. Most tumors were large (mean=21 cm.) Follow-up was available in all 55 patients (median=36 months). Forty-one tumors classified as high-grade dedifferentiated liposarcoma (HG-DDLPS) had mitotically active pleomorphic and spindle cells and foci of necrosis. They included tumors with foci of smooth muscle differentiation (N=12), osteosarcoma (N=4), and myxoid areas (N=9). Fourteen tumors classified as low-grade dedifferentiated liposarcoma (LG-DDLPS) displayed a predominantly bland, monomorphic, spindle cell population with few mitoses and scant necrosis. The Kaplan-Meier method and log-rank test were used for statistical analysis. All tumors had unequivocal foci of well-differentiated liposarcoma (WDLPS). Fluorescence in situ hybridization (FISH) detected amplification of MDM2 in 29 cases. Twenty of 41 patients (49%) with HG-DDLPS died of tumor, and two patients died with LG-DDLPS (14%). The overall survival of patients with LG-DDLPS was significantly longer (P=.02). The median survival was 113 months for the LG-DDLPS and 48 months for the HG-DDLPS. Metastases (N=4) occurred only in the high-grade tumors and were independent of the type of heterologous differentiation. Patients with HG-DDLPS were at a greater risk of earlier death. Distinction between the two groups is important for patient selection for possible adjuvant therapy.