[Alveolar soft part sarcoma in children: a clinicopathological study of 13 cases].

Objective: To investigate the clinicopathological manifestations, molecular genetic, diagnostic histology and differential diagnosis of alveolar soft part sarcoma (ASPS) in children. Methods: A total of 13 cases of ASPS diagnosed at Beijing Children's Hospital from August 2009 to November 2018 were collected. HE staining, histochemical staining for PAS and D-PAS, immunohistochemical (IHC) staining for TFE3, INI1 and CD68 and florescence in situ hybridization (FISH) for TFE3 gene translocation were performed. Results: There were four males and nine females, age ranged from 1 year and 2 months to 13 years and 8 months (mean 7.8 years); and four patients were under 5 years old. Histologically, the tumors showed a distinctive and characteristic nested or organoid growth pattern (11 cases) or solid, diffuse growth (2 cases). The tumor cells possessed abundant eosinophilic, or glycogen-rich and clear to vacuolated cytoplasm. The chromatin was relatively dispersed, with prominent and pleomorphic nucleoli; mitotic figures were rare. Vascular invasion was frequently seen. IHC staining showed specific nuclear TFE3 staining. The tumor cells were also positive for INI1,CD68 and vimentin; but were negative for MyoD1, Myogenin, CK and S-100 protein. Seven cases showed PAS and D-PAS staining, with fuchsia acicular or rod-shaped crystals in tumor cytoplasm. Nine cases showed TFE3 break-apart signals by FISH. Conclusions: ASPS is a rare soft tissue sarcoma in children. Compared with ASPA in adults, it has both similarities and unique clinicopathologic characteristics. The diagnosis needs to be confirmed by combining clinical, pathologic, IHC and genetic testing.目的： 探讨儿童腺泡状软组织肉瘤（alveolar soft part sarcoma，ASPS）的临床病理、分子遗传学特点、诊断及鉴别诊断。 方法： 对北京儿童医院2009年8月至2018年11月13例儿童ASPS病例存档切片行HE染色及组织化学染色[包括过碘酸-雪夫（PAS）染色及淀粉酶消化PAS（D-PAS染色）]。采用免疫组织化学染色检测TFE3、INI1、CD68等的表达，应用荧光原位杂交（FISH）法检测TFE3基因断裂易位情况。 结果： 13例ASPS中，男童4例，女童9例，年龄1岁2个月至13岁8个月，平均7.8岁，5岁以下4例。组织学上，11例肿瘤细胞呈腺泡状、巢状排列，2例肿瘤细胞呈实性、弥漫性生长。瘤细胞胞质嗜酸性，可见明显的空泡现象，核多形性，核仁突出，核分裂象罕见，3例可见血管浸润。免疫组织化学染色TFE3弥漫核阳性，INI1、CD68、波形蛋白阳性，MyoD1、Myogenin、细胞角蛋白、S-100蛋白等均阴性。7例PAS及D-PAS染色显示肿瘤细胞质内均可见紫红色针状或棒状结晶体。9例行FISH检测，均显示TFE3基因断裂易位。 结论： ASPS为儿童少见软组织肿瘤，肿瘤多位于深部肌肉内，瘤细胞排列成腺泡状或巢状，同时TFE3基因位点发生断裂易位，确定诊断需要结合临床、病理形态、免疫组织化学及基因检测综合考虑。.