Nonrandom expression of polypeptide hormones in pancreatic endocrine tumors. An immunohistochemical study in a case of multiple islet cell neoplasia

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Abstract
One hundred four endocrine tumors found in the body and tail of the pancreas of a patient with the Zollinger-Ellison syndrome (ZES) and multiple endocrine neoplasia (MEN-I) were investigated by immunohistochemistry for insulin, glucagon, somatostatin, pancreatic polypeptide (PP), and gastrin. The results for each tumor were scored into six grades according to the frequency of immunoreactive cells. Pancreatic polypeptide, glucagon, insulin, and somatostatin were demonstrated in 96, 80, 62, and 42 tumors, respectively. When only the higher scores of cell frequency (3–5) were considered, PP and glucagon (accounting for 71 and 49 tumors, respectively) differed markedly from insulin (two tumors) and somatostatin (0). The frequency of PP-immunoreactive cells was higher in tumors of large size whereas that of glucagon cells was higher in the smaller neoplasms. No significant associations of the tumoral hormonal expressions were found with the type of histologic structure (trabecular versus gyriform), the occurrence of stromal fibrosis, and the intrapancreatic location of the neoplasms, except for a higher number of somatostatin cells in fibrotic tumors. Gastrin-immunoreactive cells never were found in the tumors in spite of the concomitant hypergastrinemia. In conclusion, the nonrandom expression of the hormonal phenotype by the neoplastic islet cells, as shown by the immunohistochemical, semiquantitative analysis of a large number of tumors, suggests that in our MEN-I patient the genetically determined neoplasms also are affected by other mechanisms, possibly nongenetic.