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[928] Myxoid Leiomyosarcoma: A Clinicopathologic Study of Ten Cases
D Kindelberger, M Hollowell, C Otis, M Nucci. Brigham and Women
s Hospital, Boston, MA; Baystate Medical Center, Springfield, MA
Background: Myxoid leiomyosarcoma (mLMS) is a rare variant of uterine leiomyosarcoma (LMS). Few studies have examined this subtype and the majority of these represent case reports. This study assembled the largest series to date of uterine mLMSs and examined their clinicopathologic, and immunohistochemical features.
Design: Cases were identified by searching our pathology database for 
myxoid leiomyosarcoma
. Clinicopathologic features were obtained by review of the pathology reports and electronic medical record. All cases were stained with Alcian blue, desmin, smooth muscle actin (SMA), h-caldesmon (hCD), CD10, and ALK-1 protein. Immunostaining was scored with 4+ indicating > 50% staining, 3+ indicating 25-50% staining, 2+ indicating 10-25% staining, 1+ indicating staining < 10%, and 0 indicating no staining. Cytologic atypia was graded as mild, moderate, or severe (1+, 2+, or 3+, respectively). Mitotic figures were counted per 10 high power fields.
Results: 10 cases of mLMS were identified. Patients ranged in age from 37 to 62. The tumors ranged in size from 1.5 to 16 cm and all were grossly described as gelatinous. Microscopically, all tumors were myxoid (with > 50% of the tumor having myxoid stroma), which was confirmed by Alcian blue staining. All had infiltrative borders. Cytologic atypia was 1+ in 3 cases, 2+ in 4 cases and 3+ in 3 cases. The mitotic rate ranged from 1 to 25 per 10 hpf; four cases had less than 3 per 10 hpf. 6 of 10 cases showed 2+ or less staining for SMA, desmin, and h-CD. Two cases showed 4+ CD10 staining, the remaining eight showed 2+ staining. ALK-1 was negative in all cases. Followup ranged from 1 to 5 years. Five of the patients died of their disease; three are alive with recurrent disease; two are alive with no evidence of residual disease.
Conclusions: mLMS is a rare variant of uterine LMS with a similarly poor prognosis. Tumors have an infiltrative growth pattern, and the majority exhibit at least moderate cytologic atypia. Although all tumors were positive for smooth muscle markers, confirming their smooth muscle origin, expression was typically limited, being present in less < 25% of cells in half of the cases. Negativity for ALK-1 helps distinguish mLMS from inflammatory myofibroblastic tumor, a mxyoid neoplasm recently described to also occur in the uterus. Similar to other uterine smooth muscle tumors, mLMS may be diffusely positive for CD10.
Category: Gynecologic
Monday, March 26, 2007 11:00 AM
Platform Session: Section C, Monday Morning