Abstract
BACKGROUND: Pancreatic-type mixed acinar-neuroendocrine carcinoma (PMANEC) in the stomach is very rare. We report a case of PMANEC that was initially misdiagnosed as a gastric neuroendocrine tumor. CASE REPORT: A 63-year-old female was found to have a gastric mass by histology and immunohistochemistry. The tumor had a heterogenous histology, with areas resembling pancreatic acinar cell carcinoma and other areas exhibiting neuroendocrine features. Only the neuroendocrine component was present in the initial biopsy, resulting in the erroneous diagnosis of gastric neuroendocrine tumor. Evaluation of the final resected tumor revealed cells expressing pancreatic exocrine markers, including trypsin and chymotrypsin and BCL10 immune signaling adaptor. Large areas of the tumor (>30%) were also positive for chromogranin A and synaptophysin. The final diagnosis was PMANEC. CONCLUSION: This type of gastric cancer is rare and may cause diagnostic difficulty, especially if only the neuroendocrine component of the tumor is sampled in a biopsy.