[1039] Liposarcoma Arising in Uterine Lipoleiomyoma: A Report of Three Cases

AG McDonald, PD Cin, A Ganguly, S Campbell, Y Imai, AE Rosenberg, E Oliva. Massachusetts General Hospital, Boston, MA; Brigham and Women's Hospital, Boston, MA; Kobe City General Hospital, Kobe, Japan

Background: Primary sarcomas of the uterus are uncommon; leiomyosarcoma is the most frequent. Most uterine sarcomas arise de novo, with malignant transformation of a benign mesenchymal tumor being a very rare event and only reported in leiomyomas.
Design: The clinicopathologic features of 3 uterine liposarcomas arising in association with a lipoleiomyoma were studied. Immunohistochemistry for desmin, h-caldesmon, S-100 and MDM2, and fluorescence in situ hybridization (FISH) for the t(12;16) (q13;p11) were performed in all cases.
Results: Patients ranged in age from 49-70 (mean 59) years. All tumors were centered in the myometrium and ranged in size from 10 to 18.5 cm. They displayed a gelatinous cut surface with associated necrosis in two. On microscopic examination, the tumors had a well-circumscribed pushing margin. One tumor was uniformly hypocellular with prominent myxoid background and a striking delicate vascular network. Another showed alternating hypo- (myxoid) and hypercellular areas. The third tumor was uniformly hypercellular with a hyalinized background. In the myxoid areas, the cells were small and spindled with oval nuclei and inconspicuous nucleoli. In the hypercellular areas, the cells were pleomorphic with large, hyperchromatic nuclei. Mitotic activity ranged from 3 to 7/10 HPFs. Lipoblasts were present in all tumors but were more common in the hypercellular areas. Two tumors merged imperceptibly with a lipoleiomyoma (1 typical and 1 with bizarre nuclei), while the third tumor showed an infarcted area composed of mature fat admixed with hyalinized smooth muscle most consistent with an infarcted lipoleiomyoma. Tumors were classified as myxoid, mixed myxoid and pleomorphic, and pleomorphic liposarcoma. The benign and malignant adipose components were positive for S-100, while the benign smooth muscle component stained for desmin and h-caldesmon. MDM2 was positive in the two cases with a pleomorphic component. FISH analysis successfully completed in only one of three cases (pure pleomorphic liposarcoma) failed to show the t(12;16). Patients are alive and well 1, 2, and 20 years after surgery.
Conclusions: Primary liposarcomas of the uterus are extremely rare and most likely arise from malignant transformation of a lipoleiomyoma. These tumors should be added to the differential diagnosis of malignant mixed Mullerian (if pleomorphic) or myxoid mesenchymal tumors of the uterus.
Category: Gynecologic

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 167, Wednesday Afternoon