CEA-producing mucin-negative gastric signet-ring cell carcinoma with neuroendocrine markers: a case report.

Biopsy and autopsy materials excised from a 69-year-old woman were investigated. Serum carcinoembryonic antigen (CEA) showed a high value of 955 ng/mL. A plateaulike tumor was located in the gastric cardia and fundus to the entire gastric body. It showed severe proliferation and infiltration from the mucosa to the serosa. The tumor was comprised of signet-ring cells and poorly differentiated adenocarcinoma cells, which spread into the submucosa of the pylorus, duodenum, and jejunum. Signet-ring cells had a large, eccentric vesicular nucleus and a pale cytoplasmic inclusion. Poorly differentiated adenocarcinoma cells had a pleomorphic nucleus, small eosinophilic nucleolus, and abundant eosinophilic cytoplasm. Both neoplastic cells were positive for CEA, epithelial membrane antigen, Leu-7 (CD57), and neuron-specific enolase, and were negative for cytokeratin, vimentin, and periodic acid-Schiff, Alcian blue, and mucicarmine stains. Electron microscopy showed endocrine granules with a limiting membrane measuring approximately 238 nm in diameter in the cytoplasm. The authors diagnosed this patient as having mucin-negative gastric signet-ring cell carcinoma with neuroendocrine markers, which is suggested to exist among poorly differentiated adenocarcinoma, undifferentiated carcinoma, and signet-ring cell carcinoma.