Probe-based confocal laser endomicroscopy (pCLE) images of submucosal growth of a duodenal mucous neck cell adenoma.

Probe-based confocal laser endomicroscopy (pCLE) is an imaging technique that provides in vivo and real-time endomicroscopic analysis [1,2]. We show images of a duodenal mucous neck cell adenoma growing in the submucosa that was visualized by pCLE. A77-year-oldmanpresentedwith a3-mm protruding lesion in the duodenal blub (●" Fig.1). The lesionwas located on top of a submucosal elevation of approximately 1.5cm in size with a small depression. The protruding lesion, but not the submucosal elevation, was pathologically diagnosed as an adenoma. Endoscopic mucosal resection (EMR) was initially performed to resect the protruding lesion. However, an endoscopic biopsy from the post-EMR scar detected an adenoma 2months later. We performed pCLE, inserting the pCLE probe deeply into the small depression as well as the post EMR scar (●" Fig.2). Fluorescein-aided pCLE scanning demonstrated dark, small, and irregular-shaped crypts in the deep part of the lesion, suggesting growth of an adenoma (●" Fig .2d, ●" Fig.2e; ●" Video 1) [2]. In contrast, pCLE scanning of the surface showed regular-shaped villous structures, suggestive of non-neoplastic epithelium covering the lesion (●" Fig.2c;●" Video 2). Hybrid endoscopic submucosal dissection (circumferential cutting followed by snare resection) was performed to achieve en bloc resection of the entire submucosal elevation. Microscopic examination showed submucosal growth of the adenoma (●" Fig.3). Immunohistochemical assessment showed positivity for MUC5AC, MUC6, pepsinogen-I, and pepsinogen-II (●" Fig.4). Because these staining characteristics were consistent with those of mucous neck cells and primitive chief cells of the gastric fundic glands, a diagnosis of mucous neck cell adenoma of the duodenal bulb arising from ectopic gastric mucosa was made. Mucous neck cell adenomas are rare neoplasms of the stomach and duodenum [3]. The initially resected protruding lesion can be considered to be an epithelial component of the submucosal adenomatous growth. Dark, small, or irregular-shaped crypts on the pCLE scanning reflected the histological features of a submucosal growth of adenomatous tissue, providing useful information when making a decision on therapeutic strategy.