[29] Primary Retroperitoneal Liposarcomas: Mitoses in Non-Adipogenic Zones Correlate with Survival.

Shefali Chopra, Yunfeng Li, Dorina Gui, Fritz C Eilber, Sarah M Dry. UCLA, Los Angeles, CA; Tata Medical Center, Kolkata, India

Background: Non-lipogenic areas are considered evidence for dedifferentiation in liposarcomas. The significance of low grade histology in non-lipogenic areas has been controversial. We evaluated a series of retroperitoneal lipomatous tumors with primary resection at UCLA and compared histologic features with outcome.
Design: Forty-six retroperitoneal liposarcomas with clinical follow up were identified in our database. Slides were evaluated for: 1. extensive non-lipogenic areas (ExNLA) (defined as bands at least as wide as a 10X field and overall occupying 50%+ of at least one slide), 2. hypercellularity (defined as overlapping nuclei) within non-lipogenic regions and 3. maximal mitoses in 10 HPFs, with at least 50 fields counted. Cases were stratified into two groups based on cellularity: well-differentiated liposarcomas (WDL), +/- ExNLA with normocellularity (N=7) and liposarcomas +/- ExNLA with at least focal hypercellularity (N=39). The hypercellular group was subdivided into tumors with 0-4 mitoses/10 hpfs (LS0-4) (N=19) and tumors with ≥5 mitoses/10 hpfs (N=20) (LS5+). Histologic data was correlated with patient status, length of follow up and time to recurrence in all cases.
Results: Kaplan-Meier disease specific survival analysis demonstrates a statistically significant difference in survival between the LS0-4 and LS5+ groups (p=0.02). Fourteen patients died of disease (2/7 in WDL, 3/19 in LS0-4 and 9/20 in LS5+). 18 patients experienced 22 local and 1 distant (lung) recurrences (2/7 patients in WDL, 8/19 in LS0-4 and 13/20 in LS5+). Two recurrences occurred in 3 patients (1 LS0-4 and 2 LS5+) and 3 recurrences in one patient (LS0-4). One WDL transformed to LS5+ in a recurrence; no pathology was available for recurrences in 1 WDL and 3 LS0-4. ExNLA was seen in 2/7 WDL, 17/19 LS0-4 and all LS5+; the WDL were normocellular with rare mitoses (0-3/10). Kaplan-Meier analysis did not show significant survival differences between the WDL and LS0-4 groups, but analysis was limited by short follow up time in several members of the small WDL group.
Conclusions: Most (39/47, 83%) retroperitoneal liposarcomas in our series show ExNLA with or without hypercellularity. Importantly, liposarcomas with ExNLA and 5+ mitoses per 10 HPFs have statistically significant shorter survival than tumors with 0-4 mitoses. These results suggest the term “dedifferentiated” may be more appropriate for LS5+ cases only, while LS0-4 cases may be better termed “well-differentiated liposarcoma with increased cellularity”.
Category: Bone & Soft Tissue

Monday, February 28, 2011 1:00 PM

Poster Session II # 22, Monday Afternoon

 

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