The potential for
malignancy of an
islet cell tumor of the pancreas is difficult to cytologically judge when one evaluates only the primary lesion, because a malignant condition is usually determined by the presence of regional or distant
metastases. Nuclear
DNA cytometric measurements have proved helpful both in the evaluation of the malignant potential of other endocrine and nonendocrine lesions and in the determination of the "aggressiveness" of these
tumors. Thirty-six
islet cell tumors or their
metastases from 25 patients were studied. Eleven patients had
insulinomas and typical
insulinoma syndromes, and 14 others had
gastrinomas with the
Zollinger-Ellison syndrome. Tissue from each
tumor was stained by the Feulgen technique, and nuclear
DNA cytometry was performed by means of the microTICAS system designed by the Cytopathology Laboratory of the University of Chicago. Ploidy measurements of
insulinomas, taken alone, did not discriminate well between benign and malignant states. However, the single malignant
insulinoma could be clearly recognized, for it was one of only two lesions in that group with 5N-exceeding rate (5N-ER) values of 1% or greater. (5N-ER is defined as the percentage of
aneuploid nuclei with nuclear
DNA content greater than 5N.) On the other hand, seven of eight malignant
gastrinomas had ploidy values of 2.5N or greater (our definition of an
aneuploid state) and/or had 5N-ER values of 1% or greater, while five of six benign
gastrinomas had ploidy values of less than 2.5N and had 5N-ER values of 0%. In addition, the two most aggressive
tumors had the highest ploidy and 5N-ER values. Nuclear
DNA cytometric studies appear to offer promise as an aid in the evaluation of
pancreatic islet cell tumors, particularly
gastrinomas.