A Case of Grade 3 Gastric Neuroendocrine Tumor with Glandular Formation: Diagnosis and Differentiation from Gastric Mixed Neuroendocrine-Non-Neuroendocrine Neoplasm.
Makiko Kurata, Takuma Tajiri, Masataka Ueda et al.
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Case in brief
A 78-year-old man had a 4-cm submucosal gastric mass, and endoscopic ultrasound-guided fine-needle aspiration suggested a gastric neuroendocrine neoplasm. At surgery, frozen sections of peritoneal tissue were interpreted as adenocarcinoma, raising concern for a mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN). Examination of the resected tumor showed a smooth mucosal surface and organoid architecture, with rare atypia or necrosis, neuroendocrine-marker positivity, a Ki-67 index of 21%, and somatostatin receptor 2 expression. These findings supported a final diagnosis of grade 3 gastric neuroendocrine tumor with glandular formation rather than MiNEN.
What made this case unusual
Glandular formation and metastatic findings mimicked MiNEN, including an initial frozen-section interpretation of peritoneal adenocarcinoma. The final diagnosis was a grade 3 gastric neuroendocrine tumor with glandular formation, illustrating the diagnostic overlap between these entities.
Diagnostic / clinical pearl
When a gastric tumor with glandular features raises concern for MiNEN, integrate architecture and mitotic or necrotic features with neuroendocrine markers, Ki-67, somatostatin receptor 2, and Rb1; assess whether a distinct adenocarcinoma or neuroendocrine carcinoma component is present.