DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed metastatic breast cancer

• Documented expression of CD117 (c-kit) or platelet-derived growth factor receptor

  • Adequate tumor tissue from either the primary tumor and/or metastatic disease available for evaluation
• Must have received prior chemotherapy with an anthracycline (doxorubicin or epirubicin) and/or taxane (paclitaxel or docetaxel) as adjuvant or for advanced disease

• At least 1 unidimensionally measurable lesion

  • At least 20 mm by conventional techniques OR at least 10 mm by spiral CT scan
  • Bone disease may not be only source of measurable disease
  • Pleural or peritoneal ascites are not considered measurable disease
• No known brain metastases

• Hormone receptor status:

  • Not specified

PATIENT CHARACTERISTICS:

Age

• 18 and over

Sex

• Female or male

Menopausal status

• Not specified

Performance status

• ECOG 0-2 OR
• Karnofsky 60-100%

Life expectancy

• More than 12 weeks

Hematopoietic

• Absolute neutrophil count at least 1,500/mm^3
• WBC at least 3,000/mm^3
• Platelet count at least 100,000/mm^3

Hepatic

• Bilirubin normal
• AST or ALT no greater than 2.5 times upper limit of normal

Renal

• Creatinine normal OR
• Creatinine clearance at least 60 mL/min

Cardiovascular

• No symptomatic congestive heart failure
• No unstable angina pectoris
• No cardiac arrhythmia

Other

• No other uncontrolled concurrent illness
• No ongoing or active infection
• No prior allergic reaction attributed to compounds of similar chemical or biologic composition to imatinib mesylate
• No other malignancy within the past 5 years except basal cell skin cancer or carcinoma in situ of the cervix
• No psychiatric illness or social situation that would preclude study compliance
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective barrier contraception during and for 1 week after study

PRIOR CONCURRENT THERAPY:

Biologic therapy

• See Chemotherapy
• No concurrent biologic agents

Chemotherapy

• See Disease Characteristics

• No more than 2 prior chemotherapy regimens for metastatic disease

  • Therapy with high-dose regimens or bone marrow transplantation considered 1 regimen
• At least 4 weeks since prior chemotherapy (6 weeks for carmustine or mitomycin) and recovered
• No concurrent chemotherapy

Endocrine therapy

• Prior hormonal therapy for stage IV disease and/or as adjuvant therapy allowed

Radiotherapy

• At least 4 weeks since prior radiotherapy and recovered
• Prior localized radiotherapy that does not influence the signal of the evaluable lesion is allowed

Surgery

• At least 2 weeks since prior minor surgery
• At least 4 weeks since prior major surgery
• Recovered from prior surgery

Other

• Low-molecular weight heparin or heparin allowed for anticoagulation
• No concurrent warfarin
• No concurrent combination antiretroviral therapy for HIV-positive patients
• No concurrent investigational therapies or agents
• No other concurrent anticancer therapy
• No concurrent intake of cola, orange juice, grapefruit, or orange or grapefruit sections