[1243] Application of FNCLCC Grading to Uterine Smooth Muscle Neoplasms: Is STUMP Analogous to Low Grade Soft Tissue Leiomyosarcoma?

Tao Wang, Brendan Dickson, Nadia Ismiil, Golnar Rasty. University of Toronto, Toronto, Canada; Mount Sinai Hospital, Toronto, Canada; Sunnybrook Health Sciences Center, Toronto, Canada; University Health Network, Toronto, Canada

Background: Unlike soft tissue, uterine leiomyosarcoma (LMS) is not consistently graded. In the soft tissue, minimal mitotic activity, cytological atypia, and/or tumour necrosis are generally indicative of malignancy. The aforementioned criteria are used in grading and staging of sarcomas, including LMS. In contrast, the International Federation of Gynecology and Obstetrics does not incorporate grading into tumor staging criteria. We investigated the prognostic value of grading uterine LMS and smooth muscle tumours of uncertain malignancy potential (STUMP) using the Federation Nationale des Centres de Lutte Contre le Cancer (FNCLCC) criteria. We also hypothesize that uterine STUMPs will have similar grade (G) as low grade LMS of soft tissue.
Design: 63 cases of LMS and 15 cases of STUMP were retrospectively reviewed by 2 gynecologic and one soft tissue pathologist. The cases were scored based on pleomorphism, mitotic activity and necrosis by FNCLCC criteria. Follow-up and survival data was collected and a Kaplan Meier curve was plotted with stratification by grade. Univariate regression was also performed to correlate grade with survival.
Results: Of LMS's, 2 were G1 (3%), 16 were G2 (25%), and 45 were G3 (71%). For the STUMPs, 13 were G1 (87%), and 2 were G2 (13%). No deaths were reported for STUMP patients, though 1 patient with a grade 1 lesion had metastases. The 5-year overall survival was 100% for G1 lesions (including both STUMPS and LMS), 86% for G2 and 18% for G3. For LMS alone, G3 lesions fared worse than G2 with 5-year survival of 18% vs. 85% (hazard ratio 4.01, p=0.02).

Conclusions: The FNCLCC criteria can be used to stratify uterine smooth muscle lesions with multiple concerning features. In this context, most uterine STUMPs correspond to a grade of 1 by FNCLCC criteria. While no deaths were reported in this category, metastasis did occur. This is similar to outcomes reported in literature for low grade non-uterine LMS. Conversely, almost all uterine LMS were grade 2 or 3; a difference in survival was noted between G 2 and 3 LMS, suggesting prognostic value in reporting FNCLCC grade.
Category: Gynecologic & Obstetrics

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 185, Monday Morning


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