Inclusion Criteria:

- Prior written consent in participating in the study by the subject or his/her proxy
consenter.

- Japanese female >=18 years of age.

- Invasive breast cancer with stage IV disease.

- Documentation by local laboratory of ErbB2 status by immunohistochemistry (IHC) or
amplification by fluorescence in situ hybridization (FISH).

- If a taxane had been administered in the neoadjuvant or adjuvant setting, progression
must have occurred >12 months after completion of this treatment and the patients
recovered from all associated toxicities.

- Measurable lesion(s) according to RECIST criteria.

- Radiotherapy as palliative treatment for painful metastatic disease is permitted but
must have been stopped within 2 weeks prior to initiation of any investigational
treatment.

- For those patients whose disease is ER+ and/or PR+ one of the following criteria
should be met:

- Patient with visceral disease that requires chemotherapy (e.g., patients with
liver or lung metastases).

- Rapidly progressing or life threatening disease that are considered to be
inapplicable to hormonal therapy, as determined by the investigator.

- Patients who received hormonal therapy and are no longer benefiting from this
therapy and the hormonal treatment must have been stopped before the first dose
of investigational treatment.

- Subjects recovered from all the associated toxicities by prior endocrine
therapy.

- Eastern cooperative oncology group (ECOG) Performance status (PS) of 0 or 1.

- Able to swallow and retain oral medication.

- Cardiac ejection fraction within institutional range of normal as measured by
echocardiogram. MUGA scan is accepted in cases where an echocardiogram cannot be
performed or is inconclusive.

- Adequate organ function.

Exclusion Criteria:

- Pregnant or lactating females at anytime during the study.

- Received prior chemotherapy, immunotherapy, biologic therapy or anti-ErbB1/ErbB2
therapy for metastatic disease.

- History of other malignancy.

- Prior therapy with an ErbB1 and/or ErbB2 inhibitor, other than trastuzumab, in the
adjuvant setting.

- Planned concurrent anti-cancer therapy (chemotherapy, radiation therapy,
immunotherapy, biologic therapy, hormonal therapy) while taking investigational
treatment.

- Used an investigational drug within 30 days or five half-lives, whichever is longer,
preceding the first dose of investigational treatment.

- Unresolved or unstable, serious toxicity from prior administration of another
investigational drug and/or of prior anti-cancer treatment.

- Uncontrolled infection.

- Patients having at least postive antibody either to HBs or HBc.

- Patients who have had a positive HCV antibody.

- Peripheral neuropathy grade 2 or greater.

- Malabsorption syndrome, disease significantly affecting gastrointestinal function, or
resection of the stomach or small bowel. Subjects with ulcerative colitis are also
excluded.

- Dementia, altered mental status, or any psychiatric condition that would prohibit the
understanding or rendering of informed consent.

- Known history or clinical evidence of central nervous system (CNS) metastases or
leptomeningeal carcinomatosis.

- Concurrent disease or condition that would make the subject inappropriate for study
participation or any serious medical disorder that would interfere with the subject's
safety.

- Known history or concurrent condition of uncontrolled or symptomatic angina,
arrhythmias, or congestive heart failure.

- Concurrent treatment with prohibited medications.

- Known immediate or delayed hypersensitivity reaction or idiosyncrasy to drugs
chemically related to paclitaxel or lapatinib or their excipients.

- Have current active hepatic or biliary disease (with exception of patients with
Gilbert's syndrome, asymptomatic gallstones, liver metastases or stable chronic liver
disease per investigator assessment).