ERBB2 and cancer: Until very recently, emphasis has been placed on primary site TNM staging classification, the microscopic appearance of the tumor (histology and grade), and a few biomarkers, such as ER/PR, HER2, k-RAS, and b-Raf for the establishment of the status and prognosis of a cancer.  Consideration of the reaction of the patient to the cancer has at best been limited to somewhat contradictory comments about lymphocyte infiltration; it has only recently been recognized that the stromal milieu of a tumor is a major component of the host-cancer battle and, accordingly, a marker for prognosis.