The expression of a proliferating
antigen by Ki-67 immunohistochemistry was evaluated in 32 gastrointestinal
carcinoids and in 5
pancreatic islet cell tumors. In the tissue sections the number of labelled nuclei was calculated per
tumor area. The
tumors were classified as low proliferating (less than 0.3 labelled cells/mm2), medium proliferating (0.3-1 labelled cells/mm2), and high proliferating (greater than 1 labelled cell/mm2). In 26
tumors obtained from patients receiving antitumor
therapy (
alpha-interferon) the proliferative activity was decreased. In treated midgut
carcinoids the proliferative activity in metastatic tissue was significantly reduced (p less than 0.05). Though not statistically significant, primary midgut
carcinoids collected from untreated patients displayed a lower proliferative activity than liver
metastases. A survival analysis revealed that patients with
tumors displaying low proliferative activity had a better survival than those with high proliferative activity (p less than 0.05). Single cell cytofluorometric
DNA analyses showed regular diploid stem cell lines in the majority of
tumors from untreated patients (9/11 cases). No correlation was found between the calculated proliferative activity and the
DNA profile. The obtained results indicate that the expression of a proliferation
antigen by Ki-67 immunohistochemistry can be used to evaluate the
biological behavior of
neuroendocrine tumors of the digestive system and predict survival.