异位错构瘤性胸腺瘤的临床病理学观察和免疫组织化学研究

目的探讨异位错构瘤性胸腺瘤的临床病理学特征、免疫学表型和组织发生。方法对2例异位错构瘤性胸腺瘤进行临床病理学分析,采用免疫组织化学LSAB法行AE1/AE3、细胞角蛋白(CK)5、CK7、CK8、CK20、上皮膜抗原(EMA)、波形蛋白、CD5、CD10、α-平滑肌肌动蛋白(SMA)、calponin、结蛋白、CD34、S-100蛋白、CD57、胶质纤维酸性蛋白(GFAP)、甲状腺转录因子(TTF)-1和CD99标记。结果两例均发生于男性,年龄分别为20岁和40岁,因发现胸骨柄上缘肿块6个月和左锁骨上肿块2个多月就诊。肿块呈球形和卵圆形,边界清楚,最大直径分别为5cm和3cm,切面呈灰白色,质地柔软。组织学上,肿瘤由梭形细胞、上皮细胞和成熟的脂肪细胞3种成分混合组成。梭形细胞成分在2例中分别占到85%和70%,形态上类似纤维母细胞,多呈束状、编织状或席纹状排列。上皮细胞成分在两例中均占10%左右,形态上以非角化性鳞状上皮为主,可呈实性的小岛屿状、类似造釉细胞瘤的条索状和扩张的囊肿样排列,部分区域显示腺样分化,可见腺管形成。上皮细胞和梭形细胞在形态上有移行。成熟的脂肪组织呈不规则性分布,在两例肿瘤中所占的比例分别为<5%和20%。免疫组织化学标记显示,上皮细胞表达AE1/AE3、CK5、CK7、CK8和EMA,梭形细胞除CK外还表达波形蛋白、CD10和CD34,并部分表达α-SMA和calponin。两种细胞成分均不表达CK20、CD5、TTF-1、结蛋白、S-100蛋白、CD57、GFAP和CD99。结论异位错构瘤性胸腺瘤是一种好发于中青年男性锁骨上和胸锁关节附近软组织内的良性肿瘤,是一种由上皮和肌上皮组成的混合性肿瘤,可能起自于His颈窦,采用鳃原基混合瘤来命名或许更为合适。

Ectopic hamartomatous thymoma: a clinicopathological and immunohistochemical study of two cases

OBJECTIVE: To study the clinicopathological and immunohistochemical features of ectopic hamartomatous thymoma (EHT), and to discuss its histogenesis. METHODS: The clinical and pathologic features of two EHT cases of were evaluated. Immunohistochemical study was performed by LSAB method using a panel of antibodies including AE1/AE3, CK5, CK7, CK8, CK20, EMA, vimentin, CD5, CD10, alpha-SMA, calponin, desmin, CD34, S-100 protein, CD57, GFAP, TTF-1 and CD99. RESULTS: Both cases occurred in males aged 20 years and 40 years respectively. Each patient presented with a solitary mass, one located in the suprasternal fossa and the other in the left supraclavicular region for a period of 6 months and 2 months respectively. Grossly, the masses were well-circumscribed with spherical and ovoid appearance, measuring 5 cm and 3 cm in maximum diameter respectively. On cut section, they were gray-white in color and of soft consistency. Histologically, both tumors were composed of a mixture of spindle cells, epithelial cells and mature adipose tissue. The spindle cells element accounted 85% and 70% each in the two cases. They resembled fibroblasts in morphology and were arranged frequently in fascicular, woven or storiform patterns. Epithelial cells element represented nearly 10% in both cases. Most of the epithelial cells had a non-keratinization squamous appearance. They formed small solid islands and adamantinoma-like "nastomosing cords", or appeared as lining cells in large cystic spaces. In focal areas, glandular differentiation presented as small glands. A transition between the spindle cell and epithelium components could be also identified in some areas. Mature adipose tissue was irregularly distributed in the two tumors, about < 5% and 20% respectively. Immunohistochemically, the epithelial element expressed AE1/AE3, CK5, CK7, CK8 and EMA, whereas the spindle component expressed AE1/AE3, CK5, CK7, CK8, vimentin, CD10, CD34, alpha-SMA, MSA, and calponin. Both elements were negative for CK20, TTF-1, desmin, S-100 protein, CD57, GFAP and CD99. CONCLUSIONS: EHT is a benign tumor that occurs predominantly in the lower neck region of young to middle-aged males. Immunohistochemical study revealed myoepithelial differentiation of the spindle cells, suggesting EHT is a mixed tumor composed of epithelial and myoepithelial cells. EHT possibly originates from the remnants of cervical sinus of His, and therefore, may be renamed as branchial anlage mixed tumor.