Fukuhara Mitsuro, Higuchi Mitsunori, Owada Yuki, Inoue Takuya, Watanabe Yuzuru, Yamaura Takumi, Muto Satoshi, Hasegawa Takeo, Suzuki Hiroyuki
Department of Chest Surgery, Fukushima Medical University School of Medicine, Fukushima, Japan.
J Thorac Dis. 2017 Jun;9(6):1592-1597. doi: 10.21037/jtd.2017.05.22.
Microscopic thymomas, defined as epithelial proliferations smaller than 1 mm in diameter, characteristically occur in patients with myasthenia gravis without macroscopic thymic epithelial tumors. However, some clinical and pathological aspects of this entity are still unclear.
This retrospective study includes five consecutive patients who had undergone extended thymectomy for myasthenia gravis at our institution from April 2007 to March 2016 and in whom microscopic thymomas were diagnosed by histopathological examination of the resected specimens. During the same period, we performed 32 extended transsternal thymothymectomies/thymectomies in patients with myasthenia gravis, including the above five cases. We here review 18 cases of microscopic thymoma, including our five cases and 13 previously reported cases.
The incidence of previously undiagnosed microscopic thymoma in patients undergoing thymectomy for myasthenia gravis in our institution is 15.2%. Serum preoperative anti-acetylcholine receptor antibody (anti-AchR Ab) titers were abnormally high in all of our five cases h (74.4±53.3 nmol/L) and decreased significantly after surgery (11.7±13.5 nmol/L, P=0.037). We divided our cases into the following three groups: microscopic thymoma group (Group M), thymoma group (Group T) and non-thymic tumor group (Group N). The mean preoperative anti-AchR Ab titers of these groups were 74.4, 26.5, and 368 nmol/L, respectively. All these values decreased postoperatively. The mean anti-AchR Ab titer was significantly higher in Group M than in Group T (P=0.034). All five cases in Group M were found by post-operative pathological examination to have multifocal type A thymomas.
Microscopic thymomas tend to be multifocal type A thymomas. Anti-AchR Ab titers decreased significantly in all groups. It is very important to both perform complete extended thymectomies in patients with myasthenia gravis and pathological examination of thin slices of thymic tissue to maximize detection of microscopic thymomas.
显微镜下胸腺瘤定义为直径小于1mm的上皮性增生，其特征性地发生于无肉眼可见胸腺上皮肿瘤的重症肌无力患者中。然而，该实体的一些临床和病理特征仍不清楚。
这项回顾性研究纳入了2007年4月至2016年3月在我院因重症肌无力接受扩大胸腺切除术且经切除标本组织病理学检查诊断为显微镜下胸腺瘤的连续5例患者。在同一时期，我们对包括上述5例患者在内的重症肌无力患者进行了32例扩大经胸骨胸腺切除术/胸腺切除术。我们在此回顾了18例显微镜下胸腺瘤病例，包括我们的5例病例和13例先前报道的病例。
在我院因重症肌无力接受胸腺切除术的患者中，术前未诊断出的显微镜下胸腺瘤的发生率为15.2%。我们的5例患者术前血清抗乙酰胆碱受体抗体（抗AchR Ab）滴度均异常升高（74.4±53.3nmol/L），术后显著降低（11.7±13.5nmol/L，P=0.037）。我们将病例分为以下三组：显微镜下胸腺瘤组（M组）、胸腺瘤组（T组）和非胸腺肿瘤组（N组）。这些组术前抗AchR Ab滴度的平均值分别为74.4、26.5和368nmol/L。所有这些值术后均下降。M组的平均抗AchR Ab滴度显著高于T组（P=0.034）。M组的所有5例病例术后病理检查均发现为多灶性A型胸腺瘤。
显微镜下胸腺瘤倾向于多灶性A型胸腺瘤。所有组的抗AchR Ab滴度均显著下降。对重症肌无力患者进行完整的扩大胸腺切除术以及对胸腺组织薄片进行病理检查以最大程度地检测显微镜下胸腺瘤非常重要。
