Presurgical Therapy With Lapatinib to Explore Molecular Determinants of Response to EGFR/erbB2 Targeted Therapy

Inclusion Criteria: * Histologically or cytologically-confirmed by either core or fine needle biopsy primary invasive carcinoma of the breast; * AJCC T2-T3 disease (\>2.0 cm without chest wall or skin invasion) by at least one imaging modality (either mammogram, ultrasound, or MRI) - entry criteria is based on radiologic staging and not final pathologic staging; * ECOG performance status 0-1 (Karnofsky ≥ 70% * Any lymph node status, hormone receptor status, and level of erbB2 expression * No prior chemotherapy, hormonal therapy or radiation therapy to the affected breast for current or previous malignancy; * Cardiac ejection fraction \>50% or within the institutional range of normal; * Patients must have normal organ and marrow function defined as: Leukocyte count \>3000/uL; Absolute neutrophil count (ANC) ≥ 1,500/mm3, platelets \> 100,000/mm3, and hemoglobin ≥ 8 gm/dl; Serum creatinine ≤ 1.5 times ULN, or 24-hour creatinine clearance ≥ 75 cc/min; Serum bilirubin ≤ 1.5 times ULN; SGOT ≤ 2.5 times ULN; alkaline phosphatase ≤ 2.5 ULN times ULN. * The effects of lapatinib on the developing human fetus at the recommended therapeutic dose are unknown. For this reason, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she must inform her treating physician immediately. * Ability to understand and the willingness to sign written informed consent document. Exclusion Criteria: * AJCC T1, T4, or stage 4 disease; * Patients may not have undergone incisional or excisional biopsy of their tumor; * Patients may not be receiving any other investigational agents; * Absolute contraindication to MRI imaging (cardiac pacemaker or any non-removable metallic foreign object in the body); * On chronic therapy with any known inducer or inhibitor of CYP3A4 * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Pregnant or lactating women are excluded from this study because lapatinib is a tyrosine kinase inhibitor with the potential for teratogenic or abortifacient effects.