Predominant Paneth cell differentiation in an intestinal type gastric cancer

A distinct morphological variant of a diffuse type adenocarcinoma of the stomach with Paneth cell differentiation is reported. The tumor was a Borrmann's Type III carcinoma measuring 6.0 x 5.5 cm at the body along the greater curvature. It was composed of Paneth cell- and endocrine cell differentiated cancer cells in addition to tubular and poorly differentiated adenocarcinoma cells. The Paneth cell differentiation was characterized histologically by cytoplasmic distinct coarse eosinophilic granules stained red with periodic acid-Schiff and Masson trichrome reagents and reddish brown with phosphotungstic acid hematoxylin, and electron microscopically by lysozyme in cytoplasmic electron dense granules. In addition, electron microscopy revealed acid mucin globules and various intermediate forms between Paneth granules and the mucin globules which might be regarded as abortive forms of Paneth granules presumably resulting from defective incorporation of lysozyme-positive mucosubstances into acid mucin. Endocrine differentiated cancer cells consisted of serotonin-, peptide YY-, and glucagon/glicentin-positive cells. The various cell phenotypes found in the present tumor could be explained on the basis of intestinal differentiation of gastric cancer.