目的： 探讨肺微囊性纤维黏液瘤（microcystic fibromyxoma,MFM）的临床和病理组织学特征、免疫表型及鉴别诊断。方法： 分析1例肺MFM患者的临床资料,包括临床表现、病理组织学特征及免疫表型,并结合相关文献进行探讨。结果： 患者为63岁男性,常规胸部X线检查发现肺结节;胸部CT示两肺有多发的大小不等的结节灶,最大者位于左肺上叶,边界光整,增强后轻度强化。予患者行左肺上叶切除术,肉眼观察手术标本,见肿瘤位于肺外周,体积为1.5 cm×1.1 cm×0.7 cm,切面呈灰红色,质地软,边界尚清;标本切片在光学显微镜下观察,可见肿瘤边界清晰,有广泛的微囊结构形成,细胞呈梭形、星芒状,无异型性,未见核分裂相,间质富于黏液,伴丰富的小血管,见散在淋巴细胞、浆细胞、肥大细胞及巨噬细胞浸润。肿瘤旁距瘤体边缘0.2 cm处另见一小瘤灶,最大径为0.2 cm,组织形态与大者相同。肿瘤细胞波形蛋白呈弥漫强阳性,其余上皮源性、肌源性、神经源性、神经内分泌、血管内皮及间皮标志均为阴性,Ki-67低表达（<1%）。荧光原位杂交检测显示EWSR1基因未见易位。患者术后12个月及18个月时复查CT检查,均显示两肺有多发小结节,右肺结节数目略有增多及增大。结论： 肺MFM是一种罕见的肺间叶源性肿瘤,组织形态以微囊和黏液为特征,免疫组织化学（免疫组化）检测显示其表达波形蛋白,确诊提示需要综合组织学形态特征和免疫组化检查结果进行判断,目前报道的肺MFM病例虽均无肿瘤复发、转移,但本例为多发性,且影像学随访结节略有增多并增大,提示其可能具有恶性潜能。

Objective: To investigate the clinical manifestations, pathological features, immunophenotype and diffe-rential diagnosis of pulmonary microcystic fibromyxoma(MFM). Methods: The clinical manifestations, histopathological features, and immunophenotype were analyzed retrospectively in a patient diagnosed as pulmonary MFM, and the related literature was reviewed. Results: A 63-year-old man was detected to have lung nodule located in upper left lobe by routine X-ray examination. The chest CT showed multiple nodules in different sizes and the largest one located in the upper left lobe with smooth borders and mild enhancement. The resection of left upper lobe in lung was performed for the patient. Grossly,the big tumor located close to the edge of the lobe and the size was about 1.5 cm×1.1 cm×0.7 cm. It was grayish red, soft and had relatively clear border. Microscopically, the tumor had clear edge, and extensive microcapsule structures were observed. The cell showed the shapes of spindle or stellate without cellular atypia or mitotic figures. The tissue had a lot myxoid stroma, abundant small blood vessels and scattered lymphocytes, plasma cells,mast cells and macrophages. The other small tumor (maximum diameter of 0.2 cm) with similar morphology was 0.2 cm away from the larger one. Its' immunophenotype showed that the tumor cells were diffuse vimentin positive, and Ki-67 labelling index was low(<1%). The immunohistochemical markers for epithelial cells, muscle cells, nerve cells, neuroendocrine cells, vascular endothelial cells, and mesothelial cells were all negative. The chromosome translocation was not observed in EWSR1 gene by fluorescence in situ hybridization. The chest CT scans of the patient were repeated 12 and 18 months post the surgery and showed the number and size of multiple small nodules in right lung increased slightly. Conclusions: Pulmonary MFM is a rare mesenchymal tumor, and histologic structure is characterized with presence of microcapsule and myxoid stroma, and the tumor cells were vimentin positive. The diagnosis of pulmonary MFM depends on the morphologic observation and immunohistochemical staining. So far, the recurrence or metastasis has not been reportedyet, however, the imaging follow-up of this case shows the nodules slightly increased in numbers and size, which suggests that pulmonary MFM may have malignant potential.