[42] Myxoid Liposarcoma: A Clinicopathologic Study of 27 Cases of Primary Untreated Disease with Particular Focus on So-Called Transitional and Round Cell Areas.

Karen J Fritchie, Dean Wang, John R Goldblum, Steven A Lietman, Juraj Bodo, Steven D Billings, Brian P Rubin. Cleveland Clinic, OH

Background: Data suggest that round cell areas in myxoid liposarcoma (MLS) correlate with an adverse outcome, but there has been variability in the definition of round cell liposarcoma (RCLS). Very little attention has been paid to so-called transitional areas (TLS), and the impact of TLS on prognosis is not well studied.
Design: 27 cases of primary, untreated MLS were evaluated using a semi-quantitative analysis based on cell:stroma ratio, regardless of cytology. The following definitions were used: MLS <25% cell/stroma; TLS ≥25% and <50% cell/stroma; RCLS ≥50% cell/stroma. The areas assessed had to fill at least one 200X field to be included. All slides in each case were analyzed using this semi-quantitative method, resulting in a composite percentage of MLS, TLS and RCLS in each case. Adverse outcome was defined as local recurrence or distant metastasis. In addition, Ki67 nuclear stain was assessed in MLS, TLS and RCLS areas in each case.
Results: Patients with ≥5% RCLS were significantly more likely to develop distant metastasis than those with <5% RCLS (p=0.023). When partitioning patients into MLS (<5% RCLS and <5% TLS), TLS (<5% RCLS and ≥5% TLS) and RCLS (≥5% RCLS) groups, patients in the RCLS group were more likely to have distant metastasis than those in either the TLS or MLS groups (p=0.039). Although a trend towards increased metastasis was noted in the TLS group compared to the MLS group, the result was not statistically significant. Mean Ki67 scores in MLS, TLS and RCLS areas were 1.9, 6.6 and 17.5, and these differences were found to be statistically significant (p=0.004, p=0.008, p=0.003).
Conclusions: Similar to prior studies, our semi-quantitative analysis revealed that round cell differentiation portends an adverse outcome, as patients with ≥5% RCLS were significantly more likely to develop distant metastasis. Although no statistically significant increased risk for distant metastasis was noted with TLS, a larger group of cases with TLS would help to clarify the prognostic significance of these areas. Finally, Ki67 scores significantly increase from MLS to TLS to RCLS areas and were found to be statistically significant from one another, suggesting that Ki67 scores could be used as a surrogate to quantify MLS, TLS and RCLS areas.
Category: Bone & Soft Tissue

Monday, February 28, 2011 11:30 AM

Platform Session: Section F, Monday Morning


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