Neoplastic Paneth cells in the stomach. Report of two cases and review of the literature.

We report two cases of gastric lesions characterized on endoscopic biopsy specimens by the extensive proliferation of Paneth cells with neoplastic characteristics. One patient with long-standing pernicious anemia developed a large polypoid carcinoma of the stomach in which the majority of malignant glands were lined by Paneth cells showing varying degrees of differentiation. The second patient developed an irregular white patch just proximal to an old gastrojejunostomy anastomosis, which revealed numerous clusters of adenomatous tubules filled with cytoplasmic Paneth granules. The "Paneth" nature of the granules was supported by the morphological, histochemical, and ultrastructural findings. These cases are unusual since neoplastic Paneth cells occur only rarely in frank adenocarcinomas or in premalignant conditions of the stomach.