DISEASE CHARACTERISTICS: Histologically confirmed metastatic breast cancer No CNS metastases No rapidly progressing visceral disease Previously irradiated lesions(s) may be designated as measurable indicator tumor(s) only if more than 6 months since radiotherapy, patient has no other measurable disease regrowth, and bidimensionally measurable regrowth is documented within 2 months prior to study Stratum 1 (hormonal): Must be hormone receptor positive (ER or PR) Prior hormonal therapy only allowed for metastatic disease Must have progressed on last hormonal regimen Must have at least one bidimensionally measurable tumor Stratum 2 (chemotherapy): Hormone receptor positive or negative Must have progressed on or after prior chemotherapy (1-2 regimens) for metastatic disease (bone marrow transplant counts as 2 regimens) Prior hormonal therapy allowed Must have at least one bidimensionally measurable tumor Stratum 3 (tamoxifen): Must be hormone receptor positive (ER or PR) and progressing on tamoxifen No symptomatic visceral metastasis if on adjuvant tamoxifen at time of systemic recurrence Must have at least one bidimensionally measurable tumor, or lytic bone lesion which measures at least one cm in diameter Hormone receptor status: See above

PATIENT CHARACTERISTICS: Age: Over 18 Menopausal status: Not specified Performance status: ECOG 0-2 OR Karnofsky 60-100% Life expectancy: At least 3 months Hematopoietic: WBC at least 3,000/mm3 Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Fasting triglycerides within normal range Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) SGOT and/or SGPT no greater than 2.5 times ULN Concurrent medication with drugs that significantly alter hepatic metabolism (e.g., phenobarbital, phenytoin, oral azole antifungals) allowed only if dosage stable Renal: Creatinine less than 2 times ULN OR Creatinine clearance greater than 40 mL/min Concurrent medication with drugs that significantly alter renal metabolism (e.g., probenecid) allowed only if dosage stable Other: At least 5 years since any other prior invasive malignancy except basal cell and squamous cell carcinoma of the skin No serious concurrent illness that would prevent compliance No history of or clinically significant risk factors for developing pancreatitis Fasting triglycerides within normal range Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Prior monoclonal antibody HER2 therapy for metastatic disease allowed only if combined with chemotherapy or hormonal therapy and treatment failed No concurrent immunotherapy Chemotherapy: See Disease Characteristics At least 4 weeks since prior cytotoxic chemotherapy (at least 6 weeks since prior mitomycin or nitrosourea) No prior retinoid therapy for breast cancer At least 3 months since any other prior retinoid therapy except topical application for dermatological indications No concurrent chemotherapy Endocrine therapy: See Disease Characteristics At least 2 weeks since prior non-FDA approved hormonal therapy No other concurrent hormonal therapy except chronic low dose hormone replacement therapy or low dose corticosteroids for noncancer indication Radiotherapy: See Disease Characteristics Prior radiotherapy allowed Concurrent radiotherapy allowed only to non-indicator tumor(s) that do not represent new disease or disease progression Surgery: Prior surgery allowed Other: At least one month since prior investigational therapy (except hormonal) No other concurrent investigational therapy Concurrent medication with drugs that significantly alter hepatic metabolism (e.g., phenobarbital, phenytoin, oral azole antifungals) allowed only if dosage stable No more than 15,000 IU of vitamin A consumed daily