Intracellular cysts in gastric carcinoma.

Intracellular cysts were often found in the tumour cells in gastric carcinomas of intestinal as well as diffuse type in specimens from stomachs resected for gastric cancer. In the light microscope, the cysts appeared usually as solitary cytoplasmic vacuoles. In the electron microscope, the intracellular cysts were seen as round cavities, often containing homogenous or granular mucous material which stained with the periodic acid-silver methenamine (PASM)-method. Relatively long microvilli were lining the cysts and, not infrequently, abundant cytoplasmic microfilaments would surround the cyst wall. Similar cysts have been observed in a number of other tumours and, accordingly, their diagnostic significance must be considered in connection with other methods such as differential staining of cellular mucosubstances.