微结节性胸腺瘤伴淋巴样间质3例临床病理观察

目的:探讨微结节性胸腺瘤伴淋巴样间质(micronodular thymoma with lymphoid stroma,MNT)的临床病理特征.方法:通过组织学和免疫组织化学方法观察3例MNT,研究其临床病理特征,并复习文献.结果:肿瘤有纤维性假包膜,肿块内见多发性散在或局部融合的上皮性结节,由丰富淋巴细胞间质分隔,其中可见淋巴滤泡形成.上皮性结节由温和的细长形或卵圆形细胞组成,核仁不明显,结节内淋巴细胞稀少.免疫组织化学:上皮性结节内上皮细胞CKpan,CK5/6,CK19,CK8/18均阳性,Ki67约2%阳性,CD20,EMA阴性;间隔内淋巴细胞CD20,CD3,CD5,CD99,TdT均灶区阳性,p53,CD1α均散在阳性;淋巴细胞背景内CK5/6,C8/18,EMA均阴性.结论:MNT是一种罕见的胸腺肿瘤,目前WHO归于交界性,有特殊的发病部位和形态学表现,组织学及免疫组织化学有助于该肿瘤的诊断和鉴别诊断.

Clinicopathological observation of three cases of micronodular thymoma with lymphoid stroma

Objective: To investigate the clinicopathological characteristics of micronodular thymoma with lymphoid stroma (MNT). Methods: The clinicopathological characteristics and the related literature of three cases of MNT were studied by histopathological and immunohistochemical techniques. Results: All patients were asymptomatic and their thymus tumors were located in the anterior mediastinum. Histologically, the tumors with fibrous pseudocapsule were comprised of sporadic or mixed epithelioid nodules, which separated by abundant lymphoid stroma with folliculi lymphaticus. The nodules were consisted of neoplastic spindle cells in which there were not obvious nucleolus and fewer lymphocytes. Immunohistochemical studies showed positivity of the spindle tumor cells for CKpan, CK5/6, CKl9, CK8/18, Ki67 (2%) and stains for CD20, EMA were negative. Lymphocytes in the septum showed positivity for CD20, CD3, CD5, CD99, P53, CD1α, TdT. Lymphocytes in the background showed negativity for CK5/6, C8/18, EMA. Conclusion: Now MNT belongs to borderline tumor in WHO. MNT is very unusual but can be diagnosed with the characteristic morphology and immunoreactivity.