摘要目的 探讨婴儿原始黏液样间叶性肿瘤(PMMTI)的临床病理学特征、免疫表型和鉴别诊断.方法 回顾性分析3例PMMTI的临床资料、病理学形态和免疫学表型.结果 男性2例,女性1例,年龄分别为4岁、2d和3个月,均因家长发现肿块就诊,2例位于颈部,1例位于腰部,肿块最大径分别为6.5、5.5、2.8 cm.镜下肿瘤由小卵圆形、短梭形和小多边形的瘤细胞组成,胞质稀少嗜伊红色或呈空泡状,瘤细胞轻度异型性,核分裂象(0 ～2)/10 HPF.瘤细胞呈弥漫性生长,部分区域呈结节状分布,结节周边为胶原化基质.肿瘤间质呈黏液样,富含纤细的血管,1例部分区域可见小囊腔样结构.免疫组织化学染色显示瘤细胞主要表达波形蛋白,不表达平滑肌肌动蛋白、结蛋白、肌生成素、S-100蛋白、CD34和细胞角蛋白.3例均行手术切除,1例术后复发2次,与原发肿瘤相比,复发肿瘤中瘤细胞密度明显增高,异型性明显,核分裂象易见(10/10 HPF),该患儿2年后死亡;另2例术后无瘤生存.结论 PMMTI是一种好发于婴儿的少见软组织肿瘤,由原始间叶性细胞和黏液样基质组成,主要发生于躯干、头颈部和四肢,切除不净易复发,极少数可发生转移或导致患儿死亡.熟悉这一新病种有助于避免将其误诊为先天性纤维肉瘤和脂肪母细胞瘤等好发于婴幼儿的间叶性肿瘤.

abstractsObjective To study the clinicopathologic characteristics,immunophenotypes and differential diagnosis of primitive myxoid mesenchymal tumor of infancy (PMMTI).Methods The clinical data,histological features and immunohistochemic results of 3 cases of PMMTI were reviewed.Results There were 2 males and 1 female aged 4 years,2 days and 3 months respectively.The tumor occurred in the head and neck (n =2),and lumbar regions (n =1).Histologically,they were composed of ovoid,short spindled to polygonal mesenchymal cells with less eosinophilic cytoplasm,or vacuolated cytoplasm.There was mild nuclear atypia with mitotic activity of 0-2/10 HPF.In most areas,the neoplastic cells showed a diffuse growth pattern,whereas in some areas,they formed a vaguely nodular pattern with peripheral collagenized stroma.They were embedded in a myxoid stroma that contained a rich delicate vascular network.Besides,small cyst-like spaces were also present in one case.The tumor cells expressed vimentin,but not alpha smooth muscle actin,desmin,myogenin,S-100 protein,CD34 and cytokeratin.The patients underwent surgery.One patient had local recurrences twice and died 2 years later.Compared with the primary tumor,the recurrent lesions exhibited increased cellularity,marked cellular atypia and mitotic activity (10/10 HPF).The other two patients remained well with no evidence of disease at last during follow-up.Conclusions PMMTI is a rare soft tissue tumor of infancy,composed of primitive mesenchymal cells and myxoid stroma.It occurs mainly in the somatic soft tissues of the trunk,head and neck region,and the extremities,and is characterized by a high rate of local recurrence if incompletely excised.Metastasis and tumor related death may occur,albeit very rarely.Increased awareness of this novel entity will help avoid misinterpreting the lesion as a variety of other infantile mesenchymal neoplasms,including congenital fibrosarcoma and lipoblastoma.