Chief cell proliferation of the gastric mucosa mimicking early gastric cancer: an unusual variant of fundic gland polyp.

We describe a hitherto unknown lesion of gastric chief cell proliferation mimicking structurally mucosal gastric cancer. The unremarkable cytology of the cells, their very low Ki-67 index, the inclusion of occasional parietal cells and especially ultrastructural evidence of chief cell differentiation proved helpful in the differentiation from early gastric cancer. The exact classification of the alteration remains unresolved. The presence of microcysts suggests that the lesion is a variant of fundic gland polyp formation.