Carcinoid tumor of the pancreas. Ultrastructural observations of a lymph node metastasis and comparison with bronchial carcinoid

The clinical, pathologic, and ultrastructural findings from the case of a 64‐year‐old woman with a malignant endocrine tumor of the pancreas are presented. Clinically, the carcinoid syndrome was absent; however, elevated levels of blood serotonin and urine 5‐HIAA were recorded. Serum insulin, gastrin, ACTH, cortisone, and aldosterone were normal. Histologically, the tumor was consistent with a carcinoid tumor. Argentaffin stains were strongly positive. Ultrastructurally, a supraclavicular lymph node metastasis contained pleomorphic secretory granules morphologically identical to those of enterochromaffin cells and carcinoid tumors of the gastrointestinal tract. Ultrastructural comparison with a pulmonary carcinoid tumor showed both to have identical pleomorphic secretory granules.