Inclusion Criteria:

- Female, aged >/= 18 years old

- Advanced or metastatic breast cancer with overexpression of HER2

- Be able to provide written informed consent and comply with protocol requirements

- If of child-bearing potential, using adequate and medically acceptable contraception
method

- Have an ECOG performance status of 0-2 and be in stable condition

- Able to lie still on the PET scanner for approx. 1.5-2 h

- Adequate hepatic and renal function

- Patent ulnar artery or collateral arterial blood vessels

- If have CNS metastases, disease must be stable

- Subjects with CNS metastases should have at least a single 1 cm diameter lesion as
shown on contrast MRI

Exclusion Criteria:

- Subjects with brain metastases who have undergone prior CNS surgery

- Significant brain abnormalities, neurological disorder, psychiatric disorder or
previous brain damage

- Diabetes type I

- History of HIV, hepatitis B or hepatitis C infection

- Current alcohol and/or drug abuse

- Positive pregnancy test or lactation

- Malabsorption syndrome or disease affecting gastrointestinal function that may affect
intestinal absorption

- Requirement for additional concurrent anti-cancer therapy

- History of uncontrolled or symptomatic angina

- Concurrent treatment with an investigational agent or anti-cytotoxic therapy or use
within 30 days or 5 half-lives

- Known hypersensitivity reaction of idiosyncrasy to drugs chemically related to
lapatinib or its excipients

- Concurrent treatment with CYP3A4 inducers and inhibitors

- Unwillingness to refrain from consuming red wine, Seville oranges, grapefruit,
pomelo, grapefruit hybrids and their juices from 7 days before Day 1 until collection
of the final pharmacokinetic sample

- Known history of claustrophobia

- Known contraindications or likely risk of toxicity to gadlinium-based MRI contrast
media

- Presence of cardiac pacemaker, other electronic device or ferromagnetic metal foreign
bodies

- Any abnormality found on the MRI scan which, in the opinion of the investigator, may
influence the outcome of the PET scans or affect the safety of the volunteer

- Acute or active hepatic or biliary disease

- Any medical condition or circumstance making the volunteer unsuitable for
participation in the study.