Gene Product Immunophenotyping of Neuroendocrine Lung Tumors

Fifty-three neuroendocrine lung tumors (24 carcinoids, one atypical carcinoid, five large-cell neuroendocrine carcinomas, and 23 small-cell lung carcinomas) were investigated for immunocytochemical expression of several gene products, i.e., p53, Rb, bcl-2, c-kit, mdm-2, cdk-4, p21 proteins, and proliferation index as assessed by MIB-1. The goal of the study was to explore the relationships between histotypes in light of their own gene product–based immunophenotypical profiles. To this aim we applied the multiple correspondence analysis, which is an exploratory statistical multivariate technique that converts a data matrix into a particular type of graphic display in which the rows and columns are depicted as points. Such statistical analysis displayed that some categories of the gene product–based immunophenotyping variables are grouped in the plot identifying three groups: the first group related to carcinoids, the second to small-cell carcinomas, and the third to large-cell neuroendocrine carcinomas. These data support the evidence that carcinoids and small-cell carcinomas are two distinct, apparently immunogenotypically unrelated entities among neuroendocrine lung tumors and that atypical carcinoids and large-cell neuroendocrine carcinomas seem not to represent intermediate steps between them.