Composite glandular-endocrine cell carcinomas of the stomach: clinicopathologic and methylation study.

Four cases of very rare composite glandular-endocrine cell carcinoma of the stomach are presented with methylation findings. All but one of the tumors arose in the antrum and two of them were at the early stage. Each composite carcinoma was accompanied by atrophic and metaplastic gastritis in the adjacent mucosa. Three cases showed lymph nodes metastasis, and one of them showed both glandular and neuroendocrine tumor components within the metastatic nodes. Mucin stains were positive in the adenocarcinoma areas while only the neuroendocrine markers were positive in neuroendocrine tumor components. Of all seven markers tested for, p16INK4A methylation was observed in both components of one composite carcinoma and hMLH1 was methylated in the neuroendocrine tumor component within the same tumor. An additional six gastric large cell neuroendocrine carcinomas showed no methylation. Follow up of patients indicated short survival in patients with poorly differentiated neuroendocrine carcinoma components and advanced stages of tumors, while patients with well-differentiated neuroendocrine tumor components and early stages showed long disease-free survival. Our results suggest that hypermethylation of tumor suppressor genes is rare in gastric composite and neuroendocrine carcinomas, and prognosis of gastric composite carcinomas appears to be related to the histopathology of neuroendocrine components and tumor stage.