Sugita Shintaro, Kubo Terufumi, Aoyama Tomoyuki, Moriya Jun, Okuni Tsuyoshi, Wanibuchi Masahiko, Yamashita Ken, Onodera Maki, Tsujiwaki Mitsuhiro, Segawa Keiko, Sugawara Taro, Hasegawa Tadashi
Department of Surgical Pathology, Sapporo Medical University, School of Medicine, Sapporo, Hokkaido, Japan.
Department of Pathology, Sapporo Medical University, School of Medicine, Sapporo, Hokkaido, Japan.
Diagn Cytopathol. 2019 May;47(5):507-511. doi: 10.1002/dc.24142. Epub 2018 Dec 27.
Biphenotypic sinonasal sarcoma (BSNS) is a rare low-grade spindle cell sarcoma that predominantly affects middle-aged women with multiple tumors in the sinonasal tract. BSNS shows biphenotypic expression of neural and myogenic markers on immunohistochemistry (IHC) with a specific chimeric PAX3-MAML3 fusion. The cytological features of BSNS have so far not been reported. Here, we describe a case of BSNS including findings of imprint cytology, histology, IHC, and genetic analysis. A 30-year-old woman presented with a nodular tumor that completely occupied the ethmoid sinus. The tumor was resected and submitted for imprint cytology, which revealed relatively bland spindle tumor cells that had mildly enlarged oval to spindle-shaped nuclei with fine nuclear chromatin and a thin nuclear rim in a clear background. Nucleoli were inconspicuous and there was no significant nuclear atypia and pleomorphism. These cytological findings were consistent with the histology of low-grade spindle cell sarcoma in BSNS. On IHC, the tumor cells were focally positive for S-100 protein and α-smooth muscle actin; nuclear β-catenin expression was also seen. PAX3 split signals were detected in 52% of tumor cells by fluorescence in situ hybridization. Reverse transcriptase-polymerase chain reaction also identified a chimeric PAX3-MAML3 fusion gene. Based on these findings, we diagnosed the tumor as BSNS. Our findings revealed that a relatively bland spindle cell cytology with a clear background is a characteristic feature of BSNS. BSNS should therefore be differentiated from benign and bland-appearing malignant spindle cell tumors and the combination of cytology, histology, IHC, and genetic analysis facilitates the diagnosis of BSNS.
双表型鼻窦肉瘤（BSNS）是一种罕见的低级别梭形细胞肉瘤，主要影响中年女性，鼻窦内有多个肿瘤。BSNS在免疫组织化学（IHC）上显示神经和肌源性标志物的双表型表达，伴有特异性的嵌合PAX3-MAML3融合。迄今为止，尚未报道过BSNS的细胞学特征。在此，我们描述一例BSNS病例，包括印片细胞学、组织学、IHC和基因分析的结果。一名30岁女性出现一个结节状肿瘤，完全占据筛窦。肿瘤被切除并进行印片细胞学检查，结果显示相对温和的梭形肿瘤细胞，细胞核轻度增大，呈椭圆形至梭形，核染色质细腻，核膜薄，背景清晰。核仁不明显，无明显核异型性和多形性。这些细胞学发现与BSNS中低级别梭形细胞肉瘤的组织学表现一致。在IHC上，肿瘤细胞S-100蛋白和α-平滑肌肌动蛋白局灶性阳性；也可见核β-连环蛋白表达。通过荧光原位杂交在52%的肿瘤细胞中检测到PAX3分裂信号。逆转录聚合酶链反应也鉴定出嵌合的PAX3-MAML3融合基因。基于这些发现，我们将该肿瘤诊断为BSNS。我们的研究结果表明，背景清晰的相对温和的梭形细胞细胞学是BSNS的一个特征性表现。因此，BSNS应与良性和外观温和的恶性梭形细胞肿瘤相鉴别，细胞学、组织学、IHC和基因分析相结合有助于BSNS的诊断。
