A congenital ciliated epithelial cyst on the stomach of a B(6)C3F(1) mouse

Congenital anomalies of the alimentary tract are rare lesions in laboratory animals. We describe a congenital cyst attached to the greater curvature o f the forestomach in a B6C3F(1) mouse. The inner surface of the cyst was mo stly covered with cuboidal or pseudostratified ciliated epithelium and was focally covered with the Aat cuboidal epithelium. The base of the cyst appe ared to be inserted between the layers of the outer longitudinal muscle lay er of the forestomach, although no smooth muscle layer was evident in the f ree surface of the cyst wall. The cyst resembled duplication of the aliment ary tract, as it was lined with ciliated epithelium and had developed at th e greater curvature of the forestomach. Since the smooth muscle layer did n ot completely cover the whale wall and the cyst did not communicate with th e gastric lumen, the cyst was not thought to be a standard duplication but rather a simple congenital cyst.