Tamura Kaoru, Aoyagi Masaru, Wakimoto Hiroaki, Tamaki Masashi, Yamamoto Kohei, Yamamoto Masaaki, Ohno Kikuo
Department of Neurosurgery, Graduate School, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan.
J Neurooncol. 2006 Aug;79(1):67-72. doi: 10.1007/s11060-005-9117-6. Epub 2006 Apr 1.
Malignant transformation of benign epidermoid cysts is rare and their prognosis remains poor. A 56-year-old woman presented with left facial hypoesthesia and photophobia in the left eye. She had undergone removal of a benign epidermoid cyst in the cerebellopontine angle 8 years previously. Magnetic resonance imaging of the brain revealed a cystic lesion in the left cerebellopontine angle. The cyst wall was enhanced by gadolinium-DTPA. She underwent removal again and the histopathologic diagnosis was squamous cell carcinoma. Gamma knife radiosurgery was performed on the remnant lesion with a marginal dose of 15 Gy. The tumor shrank rapidly for 2 months after radiosurgery, but recurred 9 months later. She underwent radiosurgery again with a marginal dose of 12 Gy. A gradual increase in the size of the enhanced lesion was seen during the 4-month follow-up period subsequent to the second radiosurgery. Careful observation, employing serial magnetic resonance images, is necessary for incompletely resected epidermoid cysts because intervals before malignant transformation reportedly range from 3 months to 33 years. Newly identified contrast enhancement strongly indicates malignant change in epidermoid cysts. Gamma knife radiosurgery may be useful for short-term control of intracranial squamous cell carcinomas, but long-term effects are presently unknown.
良性表皮样囊肿的恶性转化罕见，其预后仍然很差。一名56岁女性出现左侧面部感觉减退和左眼畏光症状。她8年前曾接受过小脑脑桥角良性表皮样囊肿切除术。脑部磁共振成像显示左侧小脑脑桥角有一个囊性病变。囊肿壁经钆-DTPA增强。她再次接受手术切除，组织病理学诊断为鳞状细胞癌。对残余病变进行了伽玛刀放射外科治疗，边缘剂量为15 Gy。放射外科治疗后肿瘤迅速缩小2个月，但9个月后复发。她再次接受放射外科治疗，边缘剂量为12 Gy。在第二次放射外科治疗后的4个月随访期间，可见强化病变大小逐渐增加。对于未完全切除的表皮样囊肿，需要利用系列磁共振图像进行仔细观察，因为据报道恶性转化前的间隔时间从3个月到33年不等。新发现的对比增强强烈提示表皮样囊肿发生了恶性变化。伽玛刀放射外科治疗可能有助于短期控制颅内鳞状细胞癌，但目前其长期效果尚不清楚。
