Is thyrogastric disease a potential setting for oncogenesis? Gastric adenoneuroendocrine carcinoma arising from Helicobacter pylori-associated atrophic gastritis in a patient with autoimmune thyroiditis.

Gastric mixed adenoneuroendocrine carcinoma arising from Helicobacter pylori-associated multifocal atrophic gastritis is exceedingly rare. An added association with autoimmune thyroiditis in this case highlighted a complex interplay between Helicobacter, autoimmunity and gastric atrophy. A 55-year-old hypothyroid female presented with hematemesis and a large polypoidal mass in the gastric fundus, suggestive of gastrointestinal stromal tumor on imaging and endoscopy. Histopathology revealed a tumor comprised of nests of monomorphic cells immunopositive for synaptophysin and chromogranin A admixed with malignant glands. Follow-up imaging revealed a heterogeneously enhancing residual gastric body wall. A completion total gastrectomy was performed. Histopathology displayed multifocal atrophic gastritis, occasional Helicobacter and nests of neuroendocrine cells. The patient also had markedly elevated levels of anti-thyroid peroxidase and anti-thyroglobulin. To the best of our knowledge, this is the first case of gastric adenoneuroendocrine carcinoma arising from H. pylori-associated atrophic gastritis, in a patient with autoimmune thyroiditis.