The molecular analysis of human cancer is complicated by the difficulty in obtaining pure populations of tumor cells to study. One traditional method of obtaining a pure representation has been establishing cancer cell lines from primary tumors. However, this technique is time consuming and of low yield. Artifacts of cell culture include the selection of genetic alterations not present in primary tumors (1 ,1 ) and the alteration of gene expression as compared to primary tumors (3 ). When molecular techniques move from experimental to diagnostic settings, the need for robust, reproducible and “real time” testing will probably therefore require the direct analysis of tissue samples.