Surgical Pathology Criteria

Appendiceal Carcinoid / Well Differentiated Neuroendocrine Neoplasm / Tumor

Differential Diagnosis

Appendiceal Carcinoid / Well Differentiated Neuroendocrine Cell Neoplasm Appendiceal or Other GI Adenocarcinoma
Bland cytologic features Atypical cytology
Chromogranin or synaptophysin positive Chromogranin and synaptophysin negative
No desmoplastic response Desmoplastic response frequent
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 and/or signet ring cells

 

Appendiceal Carcinoid / Well Differentiated Neuroendocrine Cell Neoplasm Goblet Cell Carcinoid and/or Carcinoma ex-GCC
Chromogranin or synaptophysin positive Chromogranin and synaptophysin stain rare to scattered cells only
No intracytoplasmic mucin (lumenal mucin may be present in tubular carcinoid) Intracytoplasmic mucin in goblets
CK7 negative, CK20 variable CK7 variable, CK20 100%
Rare mitotic figures at most Mitotic figures may be numerous in carcinoma ex-GCC
Cohesive nests and cords Single cell infiltration or sheet like growth in carcinoma ex-GCC
No desmoplasia Desmoplasia may be present in carcinoma ex-GCC

 

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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