# Unveiling the Rarity: A Case of a Mixed Neuroendocrine-Non-Neuroendocrine Tumor of the Gastroesophageal Junction

## TL;DR

This paper reports a rare case of a mixed tumor at the gastroesophageal junction, diagnosed through endoscopy and confirmed with histopathology and immunohistochemistry.

## Contribution

The novelty lies in presenting a rare MiNEN tumor at the GEJ and emphasizing the diagnostic approach for such cases.

## Key findings

- A 70-year-old man was diagnosed with a mixed neuroendocrine-non-neuroendocrine tumor at the gastroesophageal junction.
- Endoscopic submucosal dissection followed by chemotherapy and radiotherapy led to no recurrence in post-treatment monitoring.
- The case underscores the importance of EGD, histopathology, and immunohistochemistry in diagnosing upper GI bleeds.

## Abstract

Mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) are a rare group of heterogeneous tumors, consisting of an endocrine and a nonendocrine component, which can develop throughout the gastrointestinal (GI) tract. This case presents a 70-year-old man with a complex medical history who initially presented with an upper GI bleed. After being stabilized, he underwent an esophagogastroduodenoscopy (EGD) that revealed a suspicious gastroesophageal junction (GEJ) mass. Histopathological studies paired with immunohistochemical investigations of the mass confirmed the rare diagnosis of MiNENs. He then underwent an endoscopic submucosal dissection (ESD) with subsequent chemotherapy and adjunct radiotherapy, with no recurrence noted on post-treatment surveillance. This case highlights the need for an EGD, histopathological examination, and immunohistochemical staining for detecting the underlying etiology of an upper GI bleed.