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Surgical Pathology Criteria

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Rectal Carcinoid / Well Differentiated Endocrine Neoplasm

WHO 2010 has changed back to usage of the term Neuroendocrine rather than Endocrine

See: Rectal Neuroendocrine Tumor (Carcinoid)

Differential Diagnosis

  • Conventional GI adenocarcinoma
  • Site of origin of metastatic well differentiated endocrine carcinoma
Rectal Carcinoid / Well Differentiated Neuroendocrine Cell Neoplasm Conventional Colorectal Adenocarcinoma
Bland cytologic features Atypical cytology
Chromogranin or synaptophysin positive Chromogranin and synaptophysin negative (scattered cells OK)
Rare mitotic figures Mitotic figures frequently numerous
Cohesive nests and cords Frequent single cell infiltration
No surface adenoma or in situ lesion May have surface adenoma or in situ component
No intracytoplasmic mucin May have intracytoplasmic mucin


Determination of common sites of origin for metastatic well differentiated endocrine neoplasms
Lung 40-50% Negative Negative Negative Negative
Pancreas Negative 0-18% 28% 68% 50-67%
Stomach Negative 0-17% 60% Negative 20%
Duodenum Negative 0-17% 60% Negative 100%
Ileum Negative >90% Negative Negative Negative
Appendix Negative >90% 55% Negative 21%
Rectum Negative 0-55% 17% Negative 85%
Detection of specific islet hormones may be useful; PAX8 data has been questioned (see Pancreas).


Determination of common sites of origin for metastatic well differentiated endocrine neoplasms-keratins
  CK7 CK20
Lung Variable Negative
Pancreas Variable Variable
Stomach Variable Negative
Duodenum Negative Variable
Ileum Negative Variable
Appendix Negative Variable
Rectum Variable Variable
CK7/20 staining is only helpful in instances of positivity where a negative result is expected


  • Five year survival for rectal carcinoid depends upon extent at presentation
    • Localized at presentation 81%
    • Regional spread at presentation 47%
    • Liver metastases at presentation 18%
    • Deaths due to disease continue to occur beyond 5 years
  • Carcinoid syndrome is rare even if the liver is involved by metastases
  • 13% of patients also have a non-endocrine neoplasm, usually gastrointestinal adenocarcinoma

Grading and Staging

  • Histopathologic features are predictive of behavior (based on AFIP; WHO does not give a concise summary)
    • Benign (but note that there are rare reports of mets)
      • Non-functioning
      • Well differentiated
      • ≤2 cm in greatest dimension
      • Confined to mucosa and submucosa
        • No involvement of muscularis propria
      • No vascular invasion
    • Uncertain malignant behavior
      • As for benign, but with:
        • Vascular invasion
    • Low grade malignant
      • Non-functioning and well differentiated, with
        • Invasion of muscularis propria or beyond and/or
        • Metastasis and/or
        • >2 cm in greatest dimension and/or
        • >2 mitotic figures per HPF (in WHO but not in AFIP)
      • OR, functioning and well differentiated
        • Any size and extent
    • Poorly differentiated neuroendocrine carcinoma is covered separately
  • AJCC TNM 7th edition now includes carcinoids of the rectum



Gastrointestinal Endocrine Cell Proliferations and Neoplasms



  • Riddell RH, Petras RE, Williams GT, Sobin LH. Tumors of the Intestines, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 32, 2003.
  • Hamilton SR, Aaltonen LA eds. Pathology and genetics of tumours of the digestive system. World Health Organization classification of tumours, Vol. 2. Lyon: IARC Press 2000.
  • Modlin IM, Sandor A. An analysis of 8305 cases of carcinoid tumors. Cancer. 1997 Feb 15;79(4):813-29.
  • Williams GT. Endocrine tumours of the gastrointestinal tract-selected topics. Histopathology. 2007 Jan;50(1):30-41.
  • Klöppel G, Anlauf M. Epidemiology, tumour biology and histopathological classification of neuroendocrine tumours of the gastrointestinal tract. Best Pract Res Clin Gastroenterol. 2005 Aug;19(4):507-17.
  • Fiocca R, Rindi G, Capella C, Grimelius L, Polak JM, Schwartz TW, Yanaihara N, Solcia E. Glucagon, glicentin, proglucagon, PYY, PP and proPP-icosapeptide immunoreactivities of rectal carcinoid tumors and related non-tumor cells. Regul Pept. 1987 Jan;17(1):9-29.
  • Federspiel BH, Burke AP, Sobin LH, Shekitka KM. Rectal and colonic carcinoids. A clinicopathologic study of 84 cases. Cancer. 1990 Jan 1;65(1):135-40.
  • Lin X, Saad RS, Luckasevic TM, Silverman JF, Liu Y. Diagnostic value of CDX-2 and TTF-1 expressions in separating metastatic neuroendocrine neoplasms of unknown origin. Appl Immunohistochem Mol Morphol. 2007 Dec;15(4):407-14.
  • Schmitt AM, Riniker F, Anlauf M, Schmid S, Soltermann A, Moch H, Heitz PU, Klöppel G, Komminoth P, Perren A. Islet 1 (Isl1) expression is a reliable marker for pancreatic endocrine tumors and their metastases. Am J Surg Pathol. 2008 Mar;32(3):420-5.
  • Moskaluk CA, Zhang H, Powell SM, Cerilli LA, Hampton GM, Frierson HF Jr.  Cdx2 protein expression in normal and malignant human tissues: an immunohistochemical survey using tissue microarrays. Mod Pathol. 2003 Sep;16(9):913-9.
  • Srivastava A, Hornick JL. Immunohistochemical staining for CDX-2, PDX-1, NESP-55, and TTF-1 can help distinguish gastrointestinal carcinoid tumors from pancreatic endocrine and pulmonary carcinoid tumors. Am J Surg Pathol. 2009 Apr;33(4):626-32.
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