Tobacco Dependence in Breast Cancer Patients Trial of Varenicline (Chantix)

Inclusion Criteria:

* MSK patients diagnosed with breast cancer or have a mass suspicious of breast cancer at the time of enrollment, as per clinician judgment or EMR;
* Self-reported current cigarette smoker (defined as daily smoking in the past seven days)
* Advised to quit smoking by their MSK physician and willing to receive smoking cessation counseling and treatment; as per self report
* Fluent in English

Exclusion Criteria:

* Patients less than 18 years of age because the safety and efficacy of varenicline have not yet been tested in children;
* Evidence of any known or suspected medical contraindications for use of varenicline (e.g., recent (within past two months) cardiovascular instability (including myocardial infarction or unstable angina; uncontrolled hypertension, significant neurological sequelae of cerebrovascular disease, or severe congestive heart failure (New York Heart Association class III or IV), severe chronic obstructive pulmonary disease; uncontrolled gastrointestinal, hepatic, or endocrine disease; or severe renal impairment.
* Self-reported evidence of significant psychiatric history (e.g., schizophrenia, unstable bipolar disorder, panic disorder, untreated major depression) sufficient, in the investigators' judgment, to preclude participation in the clinical trial;
* Self-reported evidence of recent substance abuse or heavy alcohol use (\> 14 drinks weekly) in the last 6 months;
* Self-reported recent use (in the past 30 days) or planned use of nicotine replacement therapy (NRT) or other FDA approved cessation pharmacotherapy (bupropion);
* Pre-menopausal women who are pregnant as per EMR
* Women who are breast-feeding as per self-report.