{'fraction_non_alphanumeric': 0.0426189005558987, 'fraction_numerical': 0.01173563928350834, 'mean_word_length': 5.044776119402985, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 1, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
An unusual submucosal tumor of the stomach.

Question: A 65-year-old woman was referred to our hospital for evaluation of acid reflux symptoms. Gastroduodenoscopy revealed a subepithelial lesion with intact overlying mucosa on the posterior wall of the upper body of the stomach (Figure A). Abdominal computed tomography showed a well-circumscribed, enhancing mass at the upper body of the stomach without serosal invasion (Figure B). Endoscopic ultrasonography showed a 15-mm, homogenous, hypoechoic oval mass on the submucosal layer (Figure C). Endoscopic submucosal dissection (ESD) with enucleation of the mass was performed. We incised and dissected the mucosa of the lesion with insulation tip knife (IT-2) and a hook knife. Dark brown lobulated irregular soft tissue was seen after enucleation (Figure D). The 1.5 1.0 1.0-cm mass was excised by snare. The tumor showed a lobulated external surface (Figure E). Histologically, the tumor showed multinodular plexiform growth of bland-looking spindle cells in myxoid stroma with numerous capillary-type blood vessels (Figure F, G). Immunohistochemically, the spindle cells were myofibroblastic in nature with positive reactions for vimentin and smooth muscle actin (SMA; Figure H), but negative reactions for c-kit, desmin, CD34, neurofilament and S-100 protein. The umor cells were positive for progesterone-receptor (PR). There were no mitotic figures, and Ki-67 labeling was 1%. What is the likely diagnosis? See the GASTROENTEROLOGY web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI.