Well Differentiated Pancreatic Neuroendocrine Tumor / Islet Cell Tumor
Supplemental Studies
Immunohistology
- Chromogranin, synaptophysin, CD56 or CD57 positive in >95% of cases
- Chromogranin and synaptophysin more specific
- Synaptophysin most sensitive
- Specific polypeptides may be identified
- Both normal islet and ectopic polypeptides
- Staining frequently but not always correlates with clinical syndrome and secreted product
- Frequent staining for more than one peptide
- Staining may be negative even in the presence of a secreted and active product
- PAX8 has been proposed as a marker for pancreatic islet cell tumors (Long 2010, Sangoi 2011)
- The specificity of the antibody employed has been challenged (Moreno 2011)
- CK7 and CK20 usually negative
- CK19 expression has been reported to be an independent marker of less favorable prognosis
- Applies only to WHO groups of Uncertain Behavior and Well Differentiated Pancreatic Endocrine Carcinoma
- Acinic markers trypsin, chymotrypsin and lipase may be focally positive (<25% of cells)
- If >25%, designate as mixed acinar-endocrine carcinoma
Laboratory studies
- Measurement of secreted peptide/hormone may be more useful than immunohistochemistry for defining clinical syndrome
