This is a Phase II, randomised, double-blind, placebo-controlled study. Subjects with histologically-confirmed oestrogen receptor negative (ER-), progesterone receptor negative (PgR-) primary breast cancer breast cancer will be randomly assigned in a 2:1 ratio to receive ZD1839 250 mg once daily or matching placebo for a total period of 5 weeks. Surgical intervention will take place after 4 weeks (on Day 29) and treatment will continue for 1 week after surgery.