Gene product immunophenotyping of neuroendocrine lung tumors - No linking evidence between carcinoids and small-cell lung carcinomas suggested by multivariate statistical analysis

Fifty-three neuroendocrine lung tumors (24 carcinoids, one atypical carcino id, five large-cell neuroendocrine carcinomas, and 23 small-cell lung carci nomas) were investigated for immunocytochemical expression of several gene products, i.e., p53, Rb, bcl-2, c-kit, mdm-2, cdk-4, p21 proteins, and prol iferation 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-bas ed immunophenotypical profiles. To this aim we applied the multiple corresp ondence analysis, which is an exploratory statistical multivariate techniqu e that converts a data matrix into a particular type of graphic display in which the rows and columns are depicted as points. Such statistical analysi s displayed that some categories of the gene product-based immunophenotypin g variables are grouped in the plot identifying three groups: the first gro up related to carcinoids, the second to small-cell carcinomas, and the thir d to large-cell neuroendocrine carcinomas. These data support the evidence that carcinoids and small-cell carcinomas are two distinct, apparently immu nogenotypically unrelated entities among neuroendocrine lung tumors and tha t atypical carcinoids and large-cell neuroendocrine carcinomas seem not to represent intermediate steps between them.