Carcinoid
Common sites:
- Gut mostly – appendix > ileum and small bowel
> rectum > stomach > colon
- Pancreas, lungs, biliary tree, liver
Gross features:
- Commonly bulbous swelling of the tip of the
appendix
- Intramural or submucosal masses
- Characteristically solid, yellow-tan appearance
on transaction
- Very firm
Histologic features:
- Neoplastic cells may form islands,
trabeculae/ribbons, strands, glands, or sheets
- Monotonously similar cells – minimal variation
in cell and nuclear size
- Scant, pink, granular cytoplasm
- Subnuclear
red granules may be seen in small bowel or appendix carcinoids,
especially at periphery
- Round to oval stippled (salt n pepper) nucleus
- Mitoses infrequent or absent
- Delicate intervening fibrovascular
stroma
- Grading (WHO 2010):
- NET G1 (carcinoid) (well-differentiated
endocrine tumour by WHO 2000)
- 2 per 10 HPF mitoses (count at least 50 HPFs)
- <= 2 % Ki67
- NET G2 (well-differentiated endocrine carcinoma
by WHO 2000)
- 2-20 per 10 HPF mitoses
- 3-20 % Ki67
- NEC (large cell or small cell type) (poorly
differentiated endocrine carcinoma / small cell carcinoma by WHO 2000)
- > 20 per 10 HPF mitoses
- > 20 % Ki67
- Large, poorly-formed trabeculae, nests, or
sheets
- Abundant necrosis often
- Foci of ordinary cancer in the intramucosal component of otherwise pure NECs maybe
- Small cell carcinoma:
- Large cell NEC:
- Use the higher grade if mitotic count and Ki67
category differ
- Mixed Adenoneuroendocrine
Carcinoma (MANEC):
- Both malignant gland-forming epithelial and
neuroendocrine component (at least 30% of each, arbitrarily)
- Squamous cell component rarely
- The identification in adenocarcinoma of
scattered neuroendocrine cells by IHC does not qualify
- Mixed adenoneuroendocrine
carcinoma
- Both gland-forming epithelial and neuroendocrine
- 30% of each component should be identified
(arbitrary)
- Scattered neuroendocrine cells does not
qualify
- Neuroendocrine IHC markers expressed in the
neuroendocrine component only
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Chromogranin A
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Synaptophysin
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Neuron-specific
enolase
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Molecular features:
Other features:
- Dense core bodies on EM
- Tendency for aggressive behaviour
correlates with:
- Site (appendiceal and
rectal almost never metastasize)
- Depth (> half-way through muscularis propria)
- Size (>2cm)
- Necrosis
- Mitoses
- Goblet cell carcinoid (appendix)
- Prognosis between that of carcinoid and
adenocarcinoma
References:
- Bosman et al.
WHO Classification of Tumours of the
Digestive System (2010)