Surgical Pathology Criteria

Duodenum (Psammomatous) Somatostatinoma

Differential Diagnosis

Duodenal (Psammomatous) Somatostatinoma Duodenal or Ampullary Adenocarcinoma
Round regular nuclei Nuclear atypia and pleomorphism
Very low mitotic rate Mitotic rate may be moderate to high, may have atypical forms
May have insular or trabecular pattern Insular and trabecular patterns unusual
Not associated with overlying adenoma May be associated with overlying adenoma
50% have psammoma bodies Psammoma bodies not seen
Somatostatin diffusely positive Somatostatin negative
Synaptophysin usually positive, chromogranin may be positive Synaptophysin, chromogranin negative
The frequent glandular pattern and invasion seen in somatostatinomas make this a more difficult distinction than for many other well differentiated gi endocrine neoplasms

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