Neuroendocrine neoplasms

Neuroendocrine neoplasms, also neuroendocrine tumours, are a group of tumours whose behaviour varies from benign to malignant and are found in may different sites.

These tumours arise from epithelium; thus, malignant tumours in this group are referred to as neuroendocrine carcinomas.

Use of the term carcinoid

Use of the term carcinoid is discouraged (in pathology reports), in the context of gastrointestinal pathology.

The term is still used for neuroendocrine tumours of the lung - see carcinoid tumours.

Carcinoid syndrome

Pathophysiology

• Neuroendocrine tumour -> hormone secretion (5-hydroxytryptamine + others).

Clinical

Features:

• Diarrhea, flushing and wheezing.

Pathologic findings

Classic pathologic finding:

• Fibrosis of cardiac valves (tricuspid and pulmonary).
  • Result TIPS = tricuspid insufficiency pulmonary stenosis.

Microscopic - generic

Features:

• Nests of cells - with fibrous stroma in between.
  • May have a trabecular architecture.
• Stippled chromatin AKA salt-and-pepper chromatin, coarse chromatin.
• Classically subepithelial/mural.

DDx:

• Paraganglioma.

Images:

• WC:
  • Neuroendocrine tumour - low mag. (WC).
  • Neuroendocrine tumour - intermed. mag. (WC).
  • Neuroendocrine tumour - high mag. (WC).
• www:
  • NET met to liver (upmc.edu).

Site specific

Lung

Main article: Lung_tumours#Neuroendocrine_tumours

Gastrointestinal tract

Main article: Duodenum#Neuroendocrine_tumours

WHO classification for digestive NET

Subtypes:

1. Neuroendocrine tumour G1.
2. Neuroendocrine tumour G2.
3. Neuroendocrine carcinoma, small cell type.
4. Neuroendocrine carcinoma, large cell type.
5. Mixed adenoneuroendocrine carcinoma.

Grading

Grading of NETs:

• Grade 1 (G1): < 2 mitoses/2 mm^2 or < 3% Ki-67.
• Grade 2 (G2): > 2 mitoses/2 mm^2 or > 3% Ki-67 and < 20 mitoses/2 mm^2 or < 20% Ki-67.
• Grade 3 (G3): > 20 mitoses/2 mm^2 or > 20% Ki-67.

Notes:

• Neuroendocrine carcinomas are G3 by definition.

Stomach

Divided into four types:

Tumour type	Relative prevalence	Multifocality	Size	Typical location	Clinical	Other	Histology
Type 1	~75%	yes	small (5-10 mm)	body	benign typically, female:male ~ 4:1, 50-60 years	chronic atrophic gastritis - usu. autoimmune	WDNET, WDNEC
Type 2	rare	yes	small ~15 mm	body	aggressive, ~50 years old	assoc. MEN I, hyperchlorhydia	WDNEC, WDNET
Type 3	10-15%	no	small and large	variable location	aggressive if >2.0 cm, males > females	normal gastrin levels	WDNET
Type 4	extremely rare	no	large	variable location	aggressive (mets usu. at time of Dx), males > females	elevated gastrin d/t parietal cell dysfunction	PDNEC

Notes:

• WDNET = well-differentiated neuroendocrine tumour.
• WDNEC = well-differentiated neuroendocrine carcinoma.
• PDNEC = poorly-differentiated neuroendocrine carinoma.

Pancreatic

Main article: Pancreatic neuroendocrine tumour

See also

• Basics.
• Goblet cell carcinoid.