YAP1-MAML2 Fusion as a Diagnostic Biomarker for Metaplastic Thymoma

BackgroundMetaplastic thymoma is a very rare tumor with only a few case reports documented in literature. Hence, its molecular features have not been well explored.Material and MethodsSeventeen specimens of metaplastic thymoma were sequenced and retrospectively analyzed by fluorescence in situ hybridization (FISH) and immunohistochemistry in the study. In addition, seven cases of micronodular thymoma with lymphoid stroma and nine cases of type A thymoma were also investigated.ResultsAmong these metaplastic thymomas, fifteen cases showed classical histological features, and two cases displayed characteristic micronodular-like growth patterns. DNA and RNA based next-generation sequencing identified and confirmed highly recurrent Yes Associated Protein 1 (YAP1) - Mastermind Like Transcriptional Coactivator 2 (MAML2) translocation (13/17, 76.5%) in metaplastic thymoma but not in micronodular thymoma with lymphoid stroma (0/7, 0%) and type A thymoma (0/9, 0%). In addition, six nonsense mutations were also detected in the metaplastic thymoma. FISH in microdissection specimens indicated that both epithelioid and spindle cell components harbored YAP1-MAML2 gene rearrangements.ConclusionsOur study explored the genetic alterations in epithelioid and spindle cell components in metaplastic thymoma. Furthermore, YAP1-MAML2 gene rearrangements emerged as a potential diagnostic biomarker helpful for distinguishing metaplastic thymoma from type A and micronodular thymoma with lymphoid stroma.

3D Printed Template CT-Guided 125I Seed Implantation In The Treatment Of A Patient With Giant Type A Thymoma: A Case Report

Background: Thymoma, as a malignant tumor with low incidence, is still recommended to be treated with surgery. For middle and advanced patients who can not be treated with surgery, it is recommended to use preoperative radiochemotherapy or chemotherapy. After the tumor regressed, the feasibility of surgical resection will be evaluated. As a new technique developed in recent years, 3D template CT-guided 125I seed implantation has achieved effective results in the treatment of a variety of solid tumors. Case presentation: We report a case of locally advanced giant thymoma (more than 10 cm) who received 3D template CT-guided 125I seed implantation and achieved clinical complete remission. Conclusions: It suggested that radioactive particle implantation may be a new and effective method for the nonoperative treatments of thymoma.

Sphingomonas and Phenylobacterium As Major Microbiota in Thymic Epithelial Tumors

Background Microbiota has been reported to be closely associated with carcinogenesis and cancer progression. However, its involvement in the pathology of thymoma remains unknown. In this study, we aimed to identify thymoma-specific microbiota using resected thymoma samples. Methods Nineteen thymoma tissue samples were analyzed through polymerase-chain-reaction amplification and 16S rRNA gene sequencing. The subjects were grouped according to histology, driver mutation status in the GTF2I gene, PD-L1 status, and smoking habits. To identify the taxa composition of each sample, operational taxonomic units (OTUs) were classified on the effective tags with 97% identity. The Shannon index of the 97% identity OTUs was calculated to evaluate alpha diversity. The linear discriminant analysis effect size (LEfSe) method was used to compare the relative abundances of all bacterial taxa. Results We identified 107 OTUs in the tumor tissues, which were classified into 26 genera. Sphingomonas and Phenylobacterium were identified as abundant genera in almost all samples. No significant difference was determined in the alpha diversity within these groups; however, type A thymoma exhibited higher bacterial diversity than type B thymoma. Through LEfSe analysis, we identified the following differentially abundant taxa: Bacilli, Firmicutes, and Lactobacillales in type A thymoma; Proteobacteria in type B thymoma; Gammaproteobacteria in tumors harboring the GTF2I mutation; and Alphaproteobacteria in tumors without the GTF2I mutation. Conclusions Sphingomonas and Phenylobacterium were identified as dominant genera in thymic epithelial tumors. These genera appear to comprise thymoma-specific microbiota involved in tumor progression; thus, they could serve as targets for the prevention of thymoma.