Inclusion Criteria:

- Patients must have metastatic (stage IV) or unresectable (cannot be removed by
surgery) stage III breast cancer

- Patients must have evaluable disease

- Patients may have received adjuvant chemotherapy and up to four prior chemotherapy
regimens for metastatic or locally recurrent disease and cannot have received prior
nab-paclitaxel or mifepristone therapy for metastatic disease

- Patients who are estrogen receptor (ER)- and/or progesterone receptor (PR)-positive
must have developed metastatic disease while on adjuvant hormonal therapy or have
progression of disease after at least one hormonal therapy for advanced disease) and
may have received unlimited prior hormonal therapies

- Eastern Cooperative Oncology Group (ECOG) performance status 0-2 (Karnofsky > 60%)

- Absolute neutrophil count >= 1,500/mL

- Platelets >= 100,000/mL

- Total bilirubin =< institutional upper limit of normal (ULN)

- AST (serum glutamic oxaloacetic transaminase [SGOT])/ALT (serum glutamic pyruvate
transaminase [SGPT]) =< 2.5 X institutional ULN

- Creatinine =< institutional ULN OR creatinine clearance >= 60 mL/min/1.73 m^2 for
patients with creatinine levels above institutional normal

- Morning cortisol >= institutional normal

- Negative serum or urine pregnancy test is required for women of child-bearing
potential (able to get pregnant)

- Women of child-bearing potential and men who are sexually active must agree to use
two forms of birth control prior to study entry and for the duration of study
participation

- Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

- Patients who have had chemotherapy or radiotherapy within 4 weeks prior to entering
the study or those who have not recovered from adverse events due to agents
administered more than 4 weeks earlier

- Patients may not be receiving any other investigational drugs or treatments

- Patients with known brain metastases are eligible as long as they have completed
radiation to the brain and have been off of corticosteroid therapy for at least 4
weeks

- History of allergic reactions to compounds similar to mifepristone or
paclitaxel/nab-paclitaxel; patients with a history of mild infusion reactions with
paclitaxel who were able to continue to receive paclitaxel with corticosteroid
premedications will be eligible to participate, as these cases were likely related to
Cremophor and not paclitaxel

- Mifepristone may affect the way the body processes some types of drugs so they cannot
be taken while on-study. These include but are not limited to non-steroidal
anti-inflammatory drugs (NSAIDs) or warfarin, cyclosporine, certain benzodiazepines.
The study doctor will review patient's current medications to determined if any are
prohibited from the study.

- Uncontrolled intercurrent illness or psychiatric illness/social situations that would
limit compliance with study requirements

- Pregnant women are excluded from this study; breastfeeding should be discontinued if
patient wishes to participate in the study

- Human immunodeficiency virus (HIV)-positive patients on combination antiretroviral
therapy are ineligible

- No history of long-term or ongoing short term use of corticosteroids is allowed