Carcinoid / Well Differentiated Neuroendocrine Neoplasm / Tumor of the Ileum, Distal Jejunum and Cecum
Definition
- Low grade neoplasm of the the ileum, distal jejunum or cecum demonstrating neuroendocrine differentiation
Note
- Duodenal endocrine neoplasms are covered separately
- High grade / poorly differentiated neuroendocrine carcinoma is covered separately
Alternate/historical Names
- Argentaffin carcinoma
- Midgut carcinoid
- Well differentiated (neuro-)endocrine tumor/carcinoma
Diagnostic Criteria
- Site of origin in the ileum, distal jejunum or cecum
- Most common in distal ileum
- Cecal carcinoids generally arise near the ileocecal valve and share histopathologic and clinical features with ileal carcinoids
- May be multiple in 25-30% of cases (as many as 100 tumors)
- Most cells show evidence of neuroendocrine differentiation
- Synaptophysin stain positive in nearly all cases
- Chromogranin positive in most
- Argyrophil stain positive in nearly all cases
- Argentaffin positive in most
- Neuron specific enolase, PGP9.5 and CD56 are sensitive but not specific
- Most well differentiated neoplasms exhibit characteristic cytologic and architectural features
- Round regular nuclei
- Stippled (salt and pepper) chromatin
- Moderate to abundant cytoplasm
- Various growth patterns
- Insular growth pattern
- Round nests of cells
- May palisade
- Trabecular
- Rows and strands of cells
- Cells are “stacked” with their long axis perpendicular to the long axis of the row
- Tubular
- Lined by single layer of uniform cells
- True glands with intracytoplasmic mucin not seen
- May form rosette-like pseudo-glandular structures
- True glands with intracytoplasmic mucin not seen
- Usually involves only base of crypts, leaving mucosa largely intact
- Carcinoids can be subdivided by pattern and secretory products
- Enterochromaffin (EC) cell serotonin producing carcinoid is the most common type in the small intestine (93-98%)
- Predominantly insular
- May have rosette-like pseudo-glandular structures
- May have single file pattern in desmoplastic areas
- No S100 positive sustentacular cells around nests
- (Differs from appendiceal carcinoids LINK)
- Produce serotonin and substance P
- Prostatic acid phosphatase positive in 28% of cases
- Synaptophysin and chromogranin A positive
- Argentaffin and argyrophil positive
- Frequent invasion
- Muscularis propria and serosa
- May elicit desmoplastic response
- L cell glucagon-like peptide and pancreatic polypeptide (PP/PYY) producing carcinoid is very rare in small intestine
- Predominantly tubular and/or trabecular
- Produce GLP-1, GLP-2, glycentin, oxyntomodulin, PP/PYY
- Synaptophysin positive, may be chromogranin A negative
- Chromogranin B positive (not detected by most common anti-chromogranin antibodies)
- Argyrophil positive, may be argentaffin negative
- Elastic adventitial sclerosis may occlude vessels
- Involves mesenteric arteries and veins
- May cause ischemic lesions
- Present in cases with adjacent invasive carcinoid
- Small vessels in and around primary tumor not involved
- Carcinoids arising in Meckel diverticula appear similar histopathologically and clinically to other ileal carcinoids
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting / updates: 7/27/10, 12/28/11
