[896] Smooth Muscle Neoplasms of the Urinary Bladder: A Clinicopathological Study of 51 Cases

TK Lee, H Miyamoto, AO Osunkoya, CC Guo, SW Weiss, JI Epstein. The Johns Hopkins Hospital, Baltimore; Emory University School of Medicine, Atlanta; M.D. Anderson Cancer Center, Houston

Background: We report the largest series to date examining the clinicopathological features of leiomyomas and leiomyosarcomas of the bladder.
Design: 31 leiomyomas and 20 leiomyosarcoma cases of urinary bladder from 3 tertiary care medical centers were examined. Leiomyosarcomas were subdivided into low- and high-grade based on mitotic count (≥5/10 HPF) and nuclear atypia.
Results: Mean age of patients with leiomyoma and leiomyosarcoma was 52 and 58, respectively. M:F ratio was higher with leiomyosarcoma (2:1) compared to leiomyoma (1:3), p<0.005. Leiomyomas: Notable features in leiomyomas were hyalinization (7/31), degenerative atypia (7/31), necrosis (4/31), myxoid changes (2/31), and focal fatty metaplasia (1/31), none with mucosal ulceration. Clinical follow-up was available for 24 patients (12-108 months; mean 36 months); 4 lost to follow-up and 3 recent cases. Two patients with classic leiomyoma developed local recurrences/persistence (both <1 year). None of the patients were diagnosed with leiomyosarcoma on follow-up, including 7 cases with degenerative atypia. Leiomyosarcoma: Of the 20 leiomyosarcomas, 8 were low-grade and 12 high-grade. Histologic features included epithelioid morphology (5/20; 1 entirely epithelioid), necrosis (11/20), and mucosal ulceration (7/20). Infiltration into the muscularis propria was seen predominantly as nodular with some cases exhibiting an irregular infiltrative pattern (6/10 with evaluable borders); an infiltrative pattern was not restricted to high grade lesions. Lesional heterogeneity was present in only 1 case, which showed both low-grade and high-grade areas. None of the cases of leiomyosarcomas had areas resembling leiomyoma. Follow-up was available for 15 patients with leiomyosarcoma (11-144 months; mean 47 months); 3 lost to follow-up; 2 recent cases. Only 1 patient with low-grade sarcoma experienced 2 local recurrences treated only by TUR and is currently free of disease. Disease related mortality was significantly higher in patients with high-grade compared to low-grade leiomyosarcomas (50% vs. none, respectively; p<0.001).
Conclusions: Leiomyoma (including symplastic leiomyoma) may be diagnosed on TUR without risk of underdiagnosing unsampled leiomyosarcoma. High-grade leiomyosarcomas are highly aggressive neoplasms compared to low-grade leiomyosarcomas, and grade can in general be accurately determined on TUR.
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 2:30 PM

Platform Session: Section A, Tuesday Afternoon


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