A symptom-free 47-year-old woman underwent UGI radiography and endoscopic examination of the stomach that showed an irregular polypoid lesion at the posterior wall of the middle gastric body. The polypoid lesion was diagnosed by biopsy as signet ring cell carcinoma (sig.), and distal gastrectomy was conducted. Pathologicaly, we diagnosed the lesion as undifferentiated (sig. and poorly differenciated adenocarcinoma (por.)) early gastric cancer presenting as Type I invading SM2. Generally, histological classification of elevated early gastric cancer is almost well or moderately differentiated adenocarcinoma. In many cases, undifferentiated histology such as por. or sig. exists almost exclusively as part of an elevated lesion or a restricted area of depressed components. Only 21 cases, including ours of this type of early cancer have been reported in the Japanese literature. Pathological findings indicated the involvement of collagen fiber, leiomyo fiber, and vessels forming the elevated leasion.
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