**10.5 Molecular profiling of tumors**

## *10.5.1 Traditional cancer typing*

Traditionally cancer is diagnosed and classified according to the morphological (histopathology/cytopathology) appearance of the cells and their surrounding tissue. It has limitations such as (1) it relies on a subjective review of the tissue, which is dependent on the knowledge and experience of a pathologist, and, therefore, may not be reproducible, (2) Limited ability to determine the individual recurrence risk of cancer, (3) Insufficient to reflect the complicated underlying molecular events that drive the neoplastic process and (4) Histopathology reports lack or offer very little information regarding the potential drug treatment regime to which cancer will respond. Traditional pathology reports help to determine treatment that leads to better outcomes. However, tumors with identical pathology may have different origins and respond differently to treatment.
