Autoimmune Atrophic Gastritis Revealing an Incidental Fundic Carcinoma in a 45-Year-Old Woman: A Case Report

Autoimmune atrophic gastritis is characterized by parietal cell loss, fundic gland atrophy, and intestinal or pyloric metaplasia. Patients commonly present with refractory dyspepsia and severe vitamin B12 deficiency. Although the condition increases the risk of neuroendocrine tumors and adenocarcinoma, early detection remains challenging.Case: We report a 45-year-old woman presenting with persistent epigastric pain unresponsive to therapy and severe vitamin B12 deficiency. Endoscopic biopsies performed to investigate suspected autoimmune gastritis showed fundic mucosal atrophy with antral-pyloric and intestinal metaplasia. Unexpectedly, one fragment revealed a dense cellular proliferation consistent with a poorly cohesive (signet-ring cell) adenocarcinoma infiltrating the atrophic fundic mucosa.Conclusion: This case underscores the value of systematic gastric biopsies in autoimmune gastritis, which can reveal early or incidental carcinoma. Vigilance is particularly warranted in patients with long-standing atrophic gastritis and severe vitamin B12 deficiency.