Oncogenes and oncoproteins have been shown to play an important role in the neoplastic progression of tumors. It is now evident that certain subsets of human tumors show preferential expression of specific oncogenes and oncoproteins that may in turn predict tumor morphology. The phenomenon of preferential oncogene or oncogene protein expression in certain morphologic types of tumor may help to better define the biologic behavior and aggressiveness of a given tumor, so leading to advances in the diagnosis, treatment, and understanding of human neoplasia.