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.