Carcinoma showing thymus-like differentiation (CASTLE) is a rare tumor, especially in the parotid gland. We encountered a CASTLE of the parotid gland and analyzed its clinicopathological features, as well as the genotype using whole exome sequencing (WES). Moreover, we successfully established an organoid culture cell line from the primary tumor tissue. The patient was a 23-year-old woman who underwent superficial parotidectomy with peripheral neck dissection, followed by radiotherapy. Pathologically, the resected specimen showed atypical epithelioid nests and trabeculae with squamous differentiation, separated by thick fibrous septa, accompanied by dense lymphocytes and plasma cell infiltration. Immunohistochemistry revealed that the tumor cells were positive for AE1/AE3, p40, p63, p16, CK5/6, and CD5, and the background lymphocytes were positive for CD5 and CD99. Based on these findings, the tumor was diagnosed as CASTLE. WES uncovered five nonsynonymous and splicing somatic mutations, namely, FREM2 p.Val861Phe, CLK3 p.Phe376Leu, DLGAP1 p.Lys294Asn, NOX1 p.Val165Met, and PSG9 c.430 + 4A > T. Organoid culture cells preserved the histopathological characteristics of the epithelioid component of CASTLE and harbored all five somatic mutations detected in the primary tumor. In conclusion, for the first time to the best of our knowledge, we successfully analyzed a comprehensive genotype and established an organoid culture cell line of a parotid gland CASTLE, which should serve for analyzing the nature of this rare tumor.

胸腺样癌（CASTLE）是一种罕见的肿瘤，尤其是在腮腺中。我们遇到了腮腺的CASTLE，并使用全外显子组测序（WES）分析了其临床病理特征以及基因型。此外，我们成功地从原发肿瘤组织建立了类器官培养细胞系。该患者是一名23岁的女性，她接受了腮腺浅表切除术并进行了周围颈清扫术，随后接受了放射治疗。病理上，切除的标本显示非典型上皮样巢和小梁，具鳞状分化，被厚的纤维间隔隔开，伴有密集的淋巴细胞和浆细胞浸润。免疫组织化学显示，肿瘤细胞对AE1 / AE3，p40，p63，p16，CK5 / 6和CD5呈阳性，而背景淋巴细胞则为CD5和CD99阳性。基于这些发现，该肿瘤被诊断为CASTLE。WES发现了五个非同义和剪接的体细胞突变，即FREM2 p.Val861Phe，CLK3 p.Phe376Leu，DLGAP1 p.Lys294Asn，NOX1 p.Val165Met和PSG9 c.430 + 4A>T。类器官培养细胞保留了CASTLE上皮样成分的组织病理学特征，并包含所有检测到的五个体细胞突变在原发肿瘤中。总之，就我们所知，这是我们第一次成功地分析了综合基因型并建立了腮腺CASTLE的类器官培养细胞系，该细胞系应用于分析这种罕见肿瘤的性质。