Immunoreactivity of various peptides in typical and atypical bronchopulmonary carcinoid tumours

The presence of a number of regulatory peptides (bombesin, gastrin, glucagon, somatostatin, calcitonin and ACTH) was compared in 30 typical carcinoid tumours and 27 well differentiated neuroendocrine carcinomas (atypical carcinoids) using conventional immunocytochemistry. Strong immunostaining for one or more peptide was observed in 97% of the typical carcinoids (29/30) whereas only 67% of the neuroendocrine carcinomas showed immunoreactivity. The peptide most frequently detected in typical carcinoids was bombesin (67%), while gastrin was more common in neuroendocrine carcinomas (44%). Immunoreactivity for more than one peptide was present in 33 tumours and in three cases, six different peptides were detected. The study shows that immunoreactivity to various peptides is more common in typical carcinoids than well differentiated neuroendocrine carcinomas. The significance of these findings is discussed.