Gastric cancer is common among the world, but genetic mechanisms of gastric carcinogenesis are not well understood. Gastric polypoid adenomas and flat dysplasias are regarded as precursor lesions. However, a detailed molecular study of these lesions has not been done to determine their role as precancerous lesions. We investigated mutations of the APC, beta-catenin, and K-ras genes, and microsatellite instability (MSI) status in 35 adenomas and 47 flat dysplasias without adenocarcinoma, 35 adenomas/dysplasias associated with adenocarcinomas, and 39 adenocarcinomas (20 diffuse type and 19 intestinal type). Somatic APC gene mutations were identified in 76% (59 of 78) of adenomas or flat dysplasias without associated adenocarcinoma, but in only 3% (1 of 30) of adenomas/dysplasias associated with adenocarcinoma, and in only 4% (3 of 69) of adenocarcinomas (P < 0.000001). No mutations of beta-catenin were found in adenocarcinomas, or adenomas/dysplasia without APC mutation. K-ras mutations were detected in 5% (4 of 82) of gastric adenomas/dysplasia without carcinoma, 3% (1 of 39) of adenocarcinomas without associated adenoma/dysplasia, and not in 32 adenocarcinomas with associated adenoma/dysplasia. High level of MSI (MSI-H) was more frequent in gastric adenoma/dysplasia associated with carcinoma (17%, 6 of 35) than in adenomas/dysplasia without carcinoma (3%, 2 of 75; P = 0.01). MSI-H was also more frequent in intestinal type adenocarcinoma (20%, 11 of 54) than in diffuse type (0%, 0 of 20; P = 0.03). APC gene mutations were present in six of nine (67%) of gastric adenomas/dysplasias with low level of MSI, but in none of the eight adenomas/dysplasia with MSI-H phenotype (P = 0.009). Our results indicate that somatic mutation of the APC gene plays an important role in the pathogenesis of gastric adenoma and dysplasia but has a limited role in neoplastic progression to adenocarcinoma. Gastric adenomas or dysplasias without APC mutations but with or without MSI may have a different biological behavior, and are precursors of intestinal-type of gastric adenocarcinomas.

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Primary large cell neuroendocrine carcinomas (LCNEC) of the urinary bladder are rare. Reported herein is a case of a primary, pure LCNEC occurring in a man. The patient was a 32-year-old man who presented with hematuria of 1 week's duration. On cystoscopic examination, a solitary mass measuring 3 cm in diameter was detected protruding from the anterosuperior wall of the urinary bladder. Two months after the primary transurethral resection, significant regrowth of the remnant mass was noted on CT, and the patient underwent a partial cystectomy. A diagnosis of LCNEC was made based upon histological and immunohistochemical findings. Tumor cells were positive for synaptophysin, chromogranin A, CD56, epithelial membrane antigen, and cytokeratin. Histologically, the tumor penetrated the deep muscle and perivesical fat. In spite of three cycles of chemotherapy, the patient developed multiple metastases in the lung and liver 10 months postoperatively. LCNEC of the urinary bladder are uncommon entities, which have a possible fatal outcome.

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