# A case of gastric adenocarcinoma with pyloric gland-type infiltrating submucosa

## TL;DR

This paper presents a rare case of gastric adenocarcinoma diagnosed using immunohistochemistry after endoscopic resection when biopsy was inconclusive.

## Contribution

Highlights the use of endoscopic resection and immunohistochemistry for diagnosing rare pyloric gland-type gastric adenocarcinoma.

## Key findings

- Pyloric gland-type gastric adenocarcinoma is rare and hard to diagnose with biopsy alone.
- Endoscopic resection followed by immunohistochemistry can confirm the diagnosis.
- Immunohistochemical markers like MUC5AC and MUC6 help distinguish pyloric gland-type tumors.

## Abstract

The development of immunohistochemical staining has revealed that gastric adenocarcinoma with the gastric phenotype can be divided into the foveolar, fundic gland, and pyloric gland phenotypes. Gastric adenocarcinoma of the pyloric gland type is difficult to diagnose using biopsy because of its low atypia and rarity. Herein, we describe a case of gastric adenocarcinoma of the pyloric gland type that was diagnosed immunohistochemically after endoscopic resection.

A 67-year-old man was referred to our hospital for the diagnosis and treatment of a 30-mm elevated lesion on the lesser curvature side of the middle of the gastric body. Although four biopsies were performed, it was difficult to determine whether the lesion was benign or malignant. Therefore, endoscopic submucosal dissection was performed, and the presence of tumor cells infiltrating the submucosa with venous invasions was identified. Immunohistochemical staining revealed that the tumor cells were positive for MUC5AC and MUC6 and negative for Pepsinogen I and H + /K + -ATPase. From the above findings, he was diagnosed as having gastric adenocarcinoma with pyloric gland type. The patient underwent a laparoscopic distal gastrectomy and was discharged without any adverse events.

Gastric adenocarcinoma of the pyloric gland type is a rare disease, and endoscopic resection can serve as a viable diagnostic option for this condition when it is difficult to diagnose using biopsy. Immunohistochemical pathology images can aid in the diagnosis of gastric adenocarcinoma of the pyloric gland type.