Sinonasal Smooth Muscle Cell Tumors.

Context.--Smooth muscle tumors (SMTs) of the sinonasal tracts are very rare mesenchymal neoplasms, and the literature includes very limited data correlating histologic parameters with clinical outcome. As the behavior of SMTs is site-dependent, defining applicable criteria to distinguish among low-grade leiomyosarcoma, SMT of uncertain malignant potential (SMTUMP), and cellular leiomyoma is sometimes difficult and arbitrary. Objective.--To correlate the clinicopathologic features of 12 well-differentiated sinonasal SMTs with MIB-1 index and clinical outcomes so as to better classify this group of tumors. Design.--Twelve cases of sporadic well-differentiated SMTs arising from the sinonasal tract were retrieved from both institutions. High-grade leiomyosarcomas were excluded from this analysis. The histologic parameters assessed included circumscription, mucosal ulceration, cellularity, nuclear atypia, mitotic count, necrosis, and destruction of adjacent bony structures. The histologic classification of these tumors was based on the guidelines for SMTs of deep soft tissues, using greater than 4 mitotic figures (MF)/10 high-power fields (HPF) to separate SMTUMP from leiomyosarcoma and the presence of 1 to 4 MF/10 HPF to distinguish between leiomyoma and SMTUMP. Immunostaining of MIB-1 index was performed in 7 cases with available material. Results.---This study showed a 1:1.5 male-female ratio and a mean age of 40 years (range, 20-67 years). The most frequent symptoms were nasal stuffiness and/or epistaxis. The tumors involved nasal cavity in 8 cases (67%), paranasal sinus alone in 2 cases (16.5%), and both nasal cavity and paranasal sinuses in 2 cases (16.5%). The tumors ranged in size from 0.3 to 5.5 cm (mean, 2 cm) and were classified as follows: 7 leiomyomas, 2 SMTUMPs, and 3 low-grade leiomyosarcomas. All 7 leiomyomas, 1 SMTUMP, and 1 leiomyosarcoma originated from vessel walls. Bone involvement was seen in both the SMTUMPs (1 of 2) and leiomyosarcomas (2 of... [ABSTRACT FROM AUTHOR]