Abstract
A gastric carcinoid was found in the glandular stomach of an untreated male B6C3F1 mouse of 109 weeks old. Neoplastic cells had a hyperchromatic nucleus and scant cytoplasm, and were grouped into lobules by fine connective tissue, a characteristic growth pattern of arrangement of the neuroendocrine organ. The cytoplasmic granules were argyrophilic when stained with Grimelius and Sevier-Munger stain. Immunohistochemically, the neoplastic cells were positive for neuron specific enolase and synaptophysin. In the electron microscopic examination, they contained numerous cytoplasmic granules consistent morphologically with neuroendocrine secretary granules. Metastases were present in the regional lymph nodes.
