颈部异位胸腺瘤的细针吸取细胞学诊断1例

Diagnosis of aspiration cytology of an ectopic cervical thymoma

目的探讨颈部异位胸腺瘤的细针吸取细胞形态学及临床病理特征。方法回顾性分析1例颈部异位胸腺瘤的临床资料,细胞学特征及免疫表型,并复习相关文献。结果体检B超发现甲状腺左叶下极一界清结节,MRI示肿块大小约为2 cm×1.5 cm,边界较光滑,似有包膜。未能进行明确诊断。随后穿刺细胞学涂片中见大量小淋巴细胞中散在分布少量上皮样细胞。上皮样细胞胞质丰富,核圆形或卵圆形,核仁不明显。细胞蜡块免疫标记淋巴细胞表达CD3和Td T,上皮样细胞表达CKpan和p63。细针吸取细胞学诊断为异位胸腺组织或胸腺瘤可能。肿块切除后组织病理证实为颈部异位胸腺瘤。结论颈部异位胸腺瘤比较少见,影像学方法难以诊断。我们的病例提示认识大量单一的小淋巴细胞及少量上皮细胞,可进一步行免疫组化染色鉴别诊断。

Objective To explore the clinicopathogical feature based on fine needle aspiration of ectopic cervical thymoma. Methods A retrospective clinicopathogical study was carried out in a case of ectopic cervical thymoma. The clinical features,cytological characteristics,and immunohistochemical staining results were analyzed,and the literatures were reviewed. Results Ultrasonography revealed a circumscribed mass in the left thyroid,and neck MRI revealed a 2 cm ×1. 5 cm mass with a well-defined capsule,with no definitive diagnosis. Fine-needle aspiration smear demonstrated abundant small lymphocytes mixed with scant epithelioid cells displaying round to oval nuclei and inconspicuous nucleoli with marginally more abundant cytoplasm. Immunocytochemical( IHC) stains on formalin-fixed, paraffin-embedded( FFPE) cell block sections showed lymphocytes were positive for CD3 and Td T,and epithelioid cells positive for CKpan and P63. Fine-needle aspiration cytology on this case identified ectopic thymus or ectopic thymoma. A subsequent mass excision was performed,confirming the diagnosis of ectopic thymoma. Conclusion Ectopic thymoma is rare and difficult to diagnose by means of imaging. Our case illustrates that multiple clusters of small lymphocytes admixed with scant epithelioid cells,and further immunohistochemical study with cytokeratins and lymphoid markers is needed for the differential diagnosis.