Extremely well-differentiated adenocarcinoma of the gastric cardia: a unique case with columnar cells and laminated stones.

Extremely well-differentiated adenocarcinoma (EWDA) is an unusual gastric cancer that is histologically too bland to be diagnosed as malignant neoplasm, particularly using biopsy. EWDA may be a gastric counterpart of 'adenoma malignum' or minimal deviation adenocarcinoma (MDA) in the uterine cervix; however, the clinicopathological features of EWDA remain less apparent than those of MDA. A 60-year-old male was complaining of dysphagia. He had been made aware of a small submucosal tumor in the cardia 2 years before the onset of this symptom. Endoscopic ultrasonographic examination revealed a large cardiac tumor consisting of thickened layers, as observed in Borrmann type IV. Three mucosal biopsies suggested only benign changes including adenoma and hyperplastic polyps. At the fourth biopsy, cytologically bland columnar cells were located in the submucosa along with stromal fibrosis and laminated stones. The possibility that non-neoplastic aberrant pancreas with lithiasis formed the tumor was denied at laparotomy by a frozen section that revealed benign-looking glands invading the diaphragm. Immunohistochemically the cancer glands were positive for CA19-9 and human gastric mucin, but not for p53 or MUC2. To our knowledge, this is a previously unknown combination of EWDA and psammomatous calcification in the stomach.