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Appendix

Other tumors

Carcinoid


Reviewer: Jaleh Mansouri, M.D. (see Reviewers page)
Revised: 21 December 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

See also L cell carcinoid and goblet cell carcinoid

Clinical features
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● Appendix is common site for endocrine tumors, as well as tumors with multiple directional differentiation
● Most common tumor of appendix, usually incidental (0.02% to 1.5% of all appendectomy specimens) and sporadic
● Incidence peaks at ages 20-39 years, 20 years earlier than intestinal carcinoid
● 20% of all GI carcinoids arise in appendix
● Nodal metastases and metastatic spread are rare, even with transmural extension
● 5 year survival is 85% even with regional metastases
● Rare liver metastases may be associated with carcinoid syndrome

Treatment
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● Appendectomy usually is curative if less than 1 cm
● Right hemicolectomy if > 2 cm or positive surgical margin or extremely pronounced mesoappendiceal spread
● Perineural or angiolymphatic invasion are not predictive

Prognostic factors for metastatic disease
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● Size of primary tumor (30% in tumors 2 cm or more, Arch Pathol Lab Med 1980;104:272)
● Mesoappendix invasion

Case reports
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● 28 year old woman with hereditary nonpolyposis colorectal cancer syndrome, colonic adenocarcinoma with microsatellite instability and incidental appendiceal carcinoid tumor without microsatellite instability (Hum Pathol 2004;35:1564)

Gross description
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● 70% at tip, usually < 1 cm
● Gray or yellow, well-demarcated, firm, intramural nodules that may narrow or obliterate lumen
● Proximal tumors may cause obstruction

Gross images
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Gray-yellow tumor at tip of appendix

Micro description
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● Three histologic subtypes including classic, tubular, and goblet cell types, although combined classical carcinoid and goblet cell carcinoid tumor was recently described (Am J Surg Pathol 2010;34:1163)
● May be diffusely within wall or along lumen
● Tumors arise in mucosa but bulk is usually within muscularis propria with associated fibrosis and smooth muscle hypertrophy
● Usually classic carcinoid insular growth pattern of solid islands of uniform polygonal cells with minimal pleomorphism, retraction of peripheral tumor cells from stroma
● Tumor cells often within intraappendiceal nerves; angiolymphatic invasion is common
● Cells have granular eosinophilic cytoplasm with either diffusely scattered or peripherally clumped granules
● Rarely acinar pattern, clear cell/balloon cell pattern or vacuolated cells
● No/rare mitotic activity
● May penetrate mesoappendix
● Two types of well differentiated tumors: EC cell (serotonin producing) and rarely L-cell (enteroglucagon or peptide YY producing, Hum Pathol 1990;21:773)
● Tumor cells associated with S100+ Schwann-like cells (sustentacular cells)

Micro images
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Islands of bland tumor cells; EM shows neurosecretory granules

Molecular description
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● May have 18q-, less frequently 11q-
● Usually diploid by flow cytometry

Positive stains
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● Chromogranin, neuron specific enolase, serotonin, substance P

Negative stains
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● CEA, TTF1, CK7 (usually, Hum Pathol 2001;32:1087)

End of Appendix > Other tumors > Carcinoid


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