Fine structure of experimental canine gastric carcinoma, with special reference to signet ring cells

Fine structure of poorly differentiated adenocarcinoma selectively induced in the canine stomach by a low concentration of N-ethyl-N'-nitro-N-nitrosoguanidine was studied with special reference to the so-called signet ring cells. These cells were electron microscopically classified into two groups: 1) mucin-containing cells and 2) intracellular microcyst cells. The cytoplasm of mucin-containing cells was packed with fused large and low electrondense secretory granules. In another type of signet ring cells, there were intracellular microcysts with microvilli on the internal surface. A comparison of canine and human signet ring cells revealed a close resemblance in the fine structure. Canine gastric carcinoma should be a good model for human gastric carcinoma therapeutics.