Abstract:

Objective To investigate clinicopathological features, immune phenotype, diagnosis and differential diagnosis of alveolar soft-part sarcoma (ASPS) in paranasal sinuses. Methods  Retrospective study of clinical manifestations, histopathological features and immunohistochemical features was conducted in one case of ASPS in paranasal sinuses.  Results  A 28-year-old female presented with bulging forehead for 2 months. MRI revealed a well-circumscribed lesion in left frontal and ethmoid sinuses extending to anterior skull base that showed slightly hyperintense signal on T₁WI and hypointense signal on T₂WI without obvious enhancement after contrast administration. The patient subsequently underwent endoscopic open surgery on left ethmoid and bilateral frontal sinuses and performed partial resection of the lesion. Three months after the initial surgery, the patient received reoperation for total removal of residual lesion and reconstructive surgery of anterior skull base. Adjuvant chemotherapy and radiotherapy were not administered. Histologically, the tumor was composed of epithelioid cells arranged in organoid nests and/or alveolar structures varying in size and shape, which were separated by connective tissue richly containing sinusoidal vascular channels. The tumor cells were generally large-sized, round, oval or polygonal with abundant eosinophilic granular or translucent vacuolated cytoplasm. The nuclei showed round or oval shape containing centrally placed and obvious nucleoli. The presence a lot of mono- or multi-nuclear giant cells served as another striking feature. Mitotic activities were rare. Reticular fiber staining indicated that reticular fibers surrounded the nest of tumor cells, and diastase-resistant periodic acid-Schiff (PAS)-positive crystalline inclusions were identified within the cytoplasm of tumor cells. Immunohistochemically, the tumor cells were reactive for TFE3, while were negative for glial fibrillary acidic protein (GFAP), melanophore markers [HMB45, Melan-A and S-100 protein (S-100)], and epithelial markers [cytokeratin (CK) and epithelial membrane antigen (EMA)]. Ki-67 labeling index was low (2%). The patient remained well without recurrence 15 months after the second surgery.  Conclusions  ASPS is a rare malignant tumor that tends to occur in adolescents. The tumor is predominantly located in deep soft tissues, such as legs and buttocks. ASPS of paranasal sinus and/or extending to skull base is extremely rare. The accurate diagnosis of ASPS mainly depends on histological and immunohistochemical features, and should be considered in differential diagnosis including the similar morphological pattern of primary or metastatic neoplasms. ASPS is characterized by ASPL-TFE3 gene fusions, and TFE3 protein is a specific marker for ASPS which displays nuclear labeling with TFE3 by immunohistochemistry.

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摘要：

目的 探讨腺泡状软组织肉瘤之临床病理学和免疫表型特征，以及诊断与鉴别诊断要点。方法与结果 女性患者，28 岁，前额部隆起2 个月。头部MRI 显示左侧额窦和筛窦占位性病变，累及前颅底伴左侧额窦黏液囊肿。分次行鼻内镜下左侧筛窦、双侧额窦开放和肿瘤部分切除术，以及前颅底-筛窦-额窦肿瘤全切除术和前颅底重建术。组织学特征表现为肿瘤细胞排列成大小不等的腺泡样或器官样结构，被富含血窦样腔隙的纤维结缔组织分隔；细胞体积较大，呈圆形、卵圆形或多角形，胞质丰富呈嗜伊红颗粒状或半透明空泡状，胞核呈圆形或卵圆形，核仁清晰、居中；部分肿瘤组织内可见较多的单核和多核瘤巨细胞，染色质深染，核分裂象罕见；网织纤维包绕肿瘤细胞巢；肿瘤细胞胞质内可见高碘酸-雪夫染色阳性的结晶物质；肿瘤细胞表达TFE3，不表达胶质纤维酸性蛋白、黑色素细胞标志物（HMB45、Melan-A、S-100 蛋白）和上皮细胞标志物（细胞角蛋白、上皮膜抗原），Ki-67 抗原标记指数约为2％。结论 腺泡状软组织肉瘤好发于青少年，以大腿和臀部等深部软组织受累为主，发生于鼻窦或颅内者少见。明确诊断需结合组织病理学和免疫表型特征，应注意与其他组织结构相似的原发性或转移性肿瘤相鉴别。TFE3 是腺泡状软组织肉瘤的特异性生物学标志物，ASPL-TFE3 基因融合是其细胞遗传学特征。

关键词: 肉瘤, 软组织腺泡状, 鼻窦, 免疫组织化学, 病理学