Thread by @DrMarkOng

How best to classify this gastric tumour? #GIpath

>95% of tumour is a WD NET (like picture 1), <5% shows mucin & goblet cells (pictures 2-4). Complicated by neoadjuvant chemotherapy for adenocarcinoma (presumably index biopsies looked more epithelial). IHC next tweet...

Synaptophysin -ve in epithelial component. Chromogranin strong +ve in NE component, weak in epithelial component. Ki67 high in epithelial component, low in NE component.

Are the mucin-producing areas amphicrine (dual differentiation in 1 cell) or a separate epithelial component?

Definition of mixed neuroendocrine, non-neuroendocrine neoplasm:
⏺️2 discrete components (morphologically & immunohistochemically)
⏺️Each component >30% (small cell carcinoma is an exception)

WHO book says don't diagnose MiNEN in carcinomas after neoadjuvant therapy, but this is to prevent over-calling high grade neuroendocrine components in treated tumours.

What's the best label? MiNEN? WD NET + focal amphicrine differentiation? WD NET + focal goblet cell carcinoma?

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