[72] Well-Differentiated and Dedifferentiated Liposarcomas with Prominent Myxoid Stroma: Analysis of 55 Cases

Stefano Sioletic, Christopher DM Fletcher, Jason L Hornick. Dana-Farber Cancer Institute, Boston, MA; Brigham and Women's Hospital & Harvard Medical School, Boston, MA

Background: Well-differentiated (WD) liposarcoma (LPS) has significant recurrent potential but does not metastasize; dedifferentiated (DD) LPS has a 15-20% metastatic risk. WD/DDLPS contain ring and giant marker chromosomes with amplified material from 12q13-15, resulting in overexpression of MDM2 and CDK4. Occasional cases of WD/DDLPS show prominent myxoid stroma, leading to potential confusion with other sarcoma types. Correct diagnosis is crucial, owing to marked differences in clinical behavior. We analyzed the clinicopathologic, immunohistochemical, and genetic features of WD/DDLPS with myxoid stroma.
Design: 55 LPS cases (22 WD; 33 DD) with prominent myxoid stroma were retrieved from consultation and surgical files (M/F 34/21; median age 55 yr; range 14-82 yr). Immunohistochemistry (IHC) for MDM2 and CDK4 was performed; cytogenetic findings were recorded. Clinical follow-up was obtained.
Results: Most tumors (78%) arose in the retroperitoneum or abdomen. Tumor size ranged from 2-50 cm (mean 17 cm). All tumors had a conventional adipocytic WDLPS component. In 15 WD cases, the myxoid component contained myxoid LPS-like plexiform vessels; the degree of nuclear atypia and pleomorphism distinguished such areas from myxoid LPS. Other cases showed a hypocellular myxoid spindle cell appearance with admixed adipocytes. The DDLPS cases showed a broader range of patterns in the myxoid areas. In 16 cases, myxofibrosarcoma-like curvilinear vessels were prominent. In other cases, the myxoid component ranged from relatively bland myxoid LPS-like morphology to a higher grade pleomorphic spindle cell appearance. By IHC, all 37 cases evaluated were positive for MDM2; CDK4 was positive in 64%. Cytogenetic findings in 8 cases showed ring and giant marker chromosomes. Follow-up in 30 cases (9 WD; 21 DD) ranged from 8 mo to 20 yr (mean 7 yr). All patients except 1 had local recurrences (up to 4). Only 1 patient so far with DD had distant metastases to lung. At last follow-up, 11 patients died of disease (10 with DD; 1 with WD), 1-20 yr after diagnosis.
Conclusions: WD and DDLPS with prominent myxoid stroma can resemble other sarcoma types, especially myxoid LPS and myxofibrosarcoma. Clinical presentation (large retroperitoneal or abdominopelvic tumor) is a clue to the correct diagnosis; the degree of nuclear atypia and pleomorphism excludes myxoid LPS. Thorough sampling is needed to identify a conventional WD component. In the absence of such a component, IHC for MDM2 and CDK4 and genetics can be useful to confirm the diagnosis.
Category: Bone & Soft Tissue

Monday, March 19, 2012 1:00 PM

Poster Session II # 7, Monday Afternoon


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