Endosonography with fine-needle aspiration biopsy (EUS-FNA) has become a widespreadly available clinical tool to diagnose numerous different lesions in humans. EUS-FNA is frequently used for tissue-based diagnoses such as lymphatic diseases (ranging from tuberculosis / sarcoidosis to malignant lymphoma) or solid tumors (such as pancreatic carcinoma, neuroendocrine tumors, sub-epithelial gastrointestinal tumors and others). Outcomes of EUS-FNA results, however, vary which is caused by several different factors ranging from experience of the endoscopist over technical factors such as use of stylet or suction for puncture through the skills of the cyto-pathologist who takes care of the specimen obtained by EUS-FNA. Though introduced since more than 20 years ago EUS-FNA has still not yet been perfectionized and several issues remain controversial among endoscopist. These issues include needle size and type (FNA versus TNB needles), use of a stylet and suction for FNA sampling, pure cytologic assessment versus cyto-histologic techniques, grading of the investigator´s and pathologist´s experience and improvement of EUS training for novices. In this report we briefly review the actual literature and summarize the available evidence on some controversely discussed issues. The results support the view that use of a stylet rarely aids to increase the amount of tissue obtained during EUS-FNA, whereas use of suction can be helpful in certain situations. Novel cutting needles may potentially improve number and size of core biopsies that can be rendered for special histologic tissue processing techniques. An in-room-cytopathologist not necessarily improves outcome of EUS-FNA results but may have a role during build-up of EUS units to become more successful. EUS-FNA education requires skilled endoscopists on both sides and can presumably be improved by objective testing of practical expertise by peer review and introducing objective sampling parameters. Novel techniques and equipment are about to evolve in the near future.

The gastroesophageal junction (GEJ), where squamous and columnar epithelia meet, is a hotspot for Barrett’s metaplasia development, dysbiosis and carcinogenesis. However, the mechanisms regulating GEJ homeostasis remain unclear. Here, by employing organoids, bulk and single-cell transcriptomics, single-molecule RNA in situ hybridisations and lineage tracing, we identified the spatial organisation of the epithelial, stromal compartment and the regulators that maintain the normal GEJ homeostasis. During development, common KRT8 progenitors generate committed unilineage p63/KRT5-squamous and KRT8-columnar stem cells responsible for the regeneration of postnatal esophagus and gastric epithelium that meet at GEJ. A unique spatial distribution of Wnt regulators in the underlying stromal compartment of these stem cells creates diverging Wnt microenvironments at GEJ and supports their differential regeneration. Further, we show that these tissue-resident stem cells do not possess the plasticity to transdifferentiate to the other lineage with the altered Wnt signals. Our study provides invaluable insights into the fundamental process of GEJ homeostasis and is crucial for understanding disease development.

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