Surgical Pathology Criteria

Rectal Carcinoid / Well Differentiated Neuroendocrine Neoplasm / Tumor

Differential Diagnosis

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
  TTF1 CDX2 PDX1 ISL1 PAX8
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

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