A 49-year-old woman has a history of peptic ulcer disease for which she has been treated with proton pump inhibitors. She has had nausea with vomiting for the past 2 months. Upper GI endoscopy reveals three circumscribed, round, smooth lesions in the gastric body from 1 to 2 cm in diameter. Biopsies are taken and microscopically show the lesions to consist of irregular glands that are cystically dilated and lined by flattened parietal and chief cells. No inflammation, Helicobacter pylori, metaplasia, or dysplasia is present. What is the most likely diagnosis?

**Core Concept**
The question describes a patient with a history of peptic ulcer disease treated with proton pump inhibitors, presenting with nausea, vomiting, and gastric lesions on upper GI endoscopy. The microscopic findings of cystically dilated glands lined by flattened parietal and chief cells suggest a specific type of gastric pathology.

**Why the Correct Answer is Right**
The clinical presentation and histopathological findings are consistent with gastric glandular cysts, also known as pseudocysts or cystic glandular dilation. This condition is often seen in patients with a history of long-term proton pump inhibitor (PPI) therapy. Prolonged PPI use can lead to cystic dilation of gastric glands due to the suppression of gastric acid secretion, which in turn reduces the hydrostatic pressure within the glands. The resulting cysts are lined by flattened parietal and chief cells, which are characteristic of this condition.

**Why Each Wrong Option is Incorrect**
* **Option A:** Gastrointestinal stromal tumors (GISTs) are rare, usually solitary lesions that can occur in the stomach. They are not typically characterized by cystic glandular dilation and are often associated with KIT mutations.
* **Option B:** Gastric adenocarcinoma is a malignant tumor that can present with irregular glands on histology. However, the presence of inflammation, Helicobacter pylori, metaplasia, or dysplasia, which are not mentioned in the question, would be expected in this condition.
* **Option C:** Mucosa-associated lymphoid tissue (MALT) lymphoma is a type of non-Hodgkin lymphoma that can occur in the stomach. It is often associated with Helicobacter pylori infection and would not typically present with cystically dilated glands.

**Clinical Pearl / High-Yield Fact**
Prolonged proton pump inhibitor therapy can lead to various gastrointestinal side effects, including cystic glandular dilation, which is a reversible condition that resolves with discontinuation of the medication.

**Correct Answer:** D. Gastric glandular cysts. Gastric glandular cysts, also known as pseudocysts or cystic glandular dilation.

✓ Correct Answer: A. Fundic gland polyps