第4节 脊柱平滑肌肉瘤
平滑肌肉瘤（leiomyosarcoma）是一种具有平滑肌分化倾向的恶性梭形细胞肉瘤，常见于子宫、腹膜后、盆腔、消化道等。发生于脊柱的平滑肌肉瘤极为罕见，多由腹膜后平滑肌肉瘤直接蔓延侵袭脊柱结构导致。患者临床表现无特异性，早期症状为腰背部疼痛，如肿瘤侵袭椎管及（或）周围神经根，则可有相应的临床表现。
脊柱平滑肌肉瘤的影像学表现亦缺乏特异性，X线表现可分为三种类型：溶骨型、混合型和囊肿型，以溶骨型破坏多见。CT检查可见骨皮质筛孔样破坏，周围可见软组织肿块，增强扫描可见均匀或不均匀强化。MRI可以很好地显示软组织肿瘤的形态及范围，平滑肌肉瘤患者T1WI呈等信号，T2WI呈混杂、不均匀稍高信号，脂肪抑制T2WI呈稍高信号；增强扫描后强化明显，但病灶内同时可见无强化区（图27-12）。
平滑肌肉瘤瘤体质软，外有包膜，切面呈灰白色鱼肉状，内部可见出血坏死结节。镜下可见梭形细胞交织形成的结节，细胞聚集成团或被纤维组织分割成多个细胞团，是平滑肌肉瘤最明显的特征。肿瘤细胞膜清楚，胞质嗜伊红染色明显，可见肌原纤维。低分化区肿瘤细胞表现为多形性，核分裂象多见，可见瘤巨细胞，失去平滑肌细胞形态和排列方式。
治疗以手术切除为主，与其他恶性软组织肉瘤相类似，肿瘤易复发，因此需强调肿瘤的彻底切除。目前缺乏有效的辅助治疗措施。
图27-12 48岁女性，C2平滑肌肉瘤
A. 术前颈椎正位片；B. 术前颈椎侧位片示C2椎板及棘突形态改变；C. CT横断面示C2左侧椎板破坏，后方有团块软组织；D. 增强MRI横断面示C2左侧椎体、附件破坏，信号异常；E. 增强MRI冠状面示C2、C3左侧肿瘤组织侵犯，形态改变；F. 增强MRI矢状面示C2椎体、C3上部分附件信号改变；G. 术后颈椎正位片；H. 术后颈椎侧位片示C2、C3附件切除枕颈固定，C2前方椎体切除钛网植骨固定
（刘铁龙 王静 高欣）
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