Razack Rubina, Bishop Justin A, Alwan Julandi, Coetzee Liezel, De Wet Daniel Rudolph, Mahomed Wasim, Merven Marc, Schubert Pawel Tomasz, Afrogheh Amir
Division of Anatomical Pathology, Tygerberg Hospital, National Health Laboratory Service, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.
Department of Pathology, University of Texas Southwestern, Medical Center, Clements University Hospital, Dallas, Texas, USA.
Acta Cytol. 2024;68(6):516-524. doi: 10.1159/000541997. Epub 2024 Oct 14.
Microsecretory adenocarcinoma (MSA) is a novel entity defined by distinctive histology, a specific immunophenotype, and unique molecular fusion MEF2C::SS18. It occurs mainly in intra-oral minor salivary glands and the skin, with only one reported case affecting the parotid gland. To the best of our knowledge, no cytomorphological features of MSA have been published to date. We report the first case of fine-needle aspiration biopsy (FNAB) cytology of MSA diagnosed in the parotid gland.
A 48-year-old man presented with a 3.5 × 2.5-cm parotid mass. FNAB of the tumour revealed a cellular smear comprising a predominantly epithelial cell population showing luminal differentiation with secretory features and a distinctive background matrix with both myxoid and mucinous qualities. Scattered, but conspicuous multinucleated giant cells were present, a feature not commonly observed in salivary gland aspirates. Histology of the excised tumour revealed classic features of MSA with supportive immunohistochemistry and SS18 break apart fusion detected by fluorescence in situ hybridisation (FISH). Next-generation sequencing confirmed a MEF2C::SS18 gene fusion.
MSA is a rare neoplasm and should be considered in the cytological differential diagnosis of low-grade salivary gland neoplasms. Its unique cytomorphological features should raise the possibility of MSA in salivary gland FNABs. The diagnosis can be established on cellular cell block preparations using immunohistochemistry and FISH or PCR.
微分泌腺癌（MSA）是一种新定义的实体肿瘤，具有独特的组织学特征、特定的免疫表型和独特的分子融合MEF2C::SS18。它主要发生于口腔内小唾液腺和皮肤，仅有1例报道发生于腮腺。据我们所知，迄今为止尚未发表过MSA的细胞形态学特征。我们报告首例经细针穿刺活检（FNAB）细胞学诊断的腮腺MSA病例。
一名48岁男性患者，腮腺出现一个3.5×2.5 cm大小的肿块。对该肿瘤进行FNAB检查，细胞涂片显示细胞成分主要为上皮细胞，呈管腔样分化，具有分泌特征，背景基质独特，兼具黏液样和黏液性特质。可见散在但明显的多核巨细胞，这一特征在唾液腺穿刺物中并不常见。切除肿瘤的组织学检查显示具有MSA的典型特征，免疫组化结果支持诊断，荧光原位杂交（FISH）检测到SS18分离融合。二代测序证实存在MEF2C::SS18基因融合。
MSA是一种罕见肿瘤，在低级别唾液腺肿瘤的细胞学鉴别诊断中应予以考虑。其独特的细胞形态学特征应提高在唾液腺FNAB中诊断MSA的可能性。可通过免疫组化、FISH或PCR在细胞块制备上进行诊断。
