Inclusion Criteria:

- Histologically confirmed endometrial adenocarcinoma

- Advanced, recurrent, or persistent disease

- Refractory to curative therapy

- HER2/neu gene amplification by fluorescent in situ hybridization

- Measurable disease

- Previously irradiated field as sole site of measurable disease allowed if
evidence of progression since completion of radiotherapy

- Performance status - GOG 0-2

- Absolute neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- Bilirubin ≤ 1.5 times upper limit of normal (ULN)

- Creatinine ≤ 1.5 times ULN

- LVEF ≥ 45% by echocardiogram or MUGA

- History of coronary artery disease and/or congestive heart failure allowed if medical
management of condition has been stable within the past 6 months

- No active or unstable cardiac disease

- No active angina

- No myocardial infarction within the past 6 months

- No requirement for supplemental oxygen at rest or with ambulation

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No active infection requiring antibiotics

- No uncontrolled infection

- No other invasive malignancy within the past 5 years except nonmelanoma skin cancer

- No other unstable medical condition that would preclude study participation

- At least 3 weeks since prior biologic and immunologic agents directed at the
malignant tumor

- No prior anti-HER2 monoclonal antibody preparation

- No other concurrent immunotherapy

- Recovered from prior chemotherapy

- Multiple prior chemotherapy regimens allowed

- No more than 320 mg/m^2 total dose of prior doxorubicin allowed (including
doxorubicin HCl liposome or other liposomally encapsulated doxorubicin preparations)

- No concurrent chemotherapy

- At least 1 week since prior hormonal therapy directed at the malignant tumor

- No concurrent hormonal therapy

- Continuation of hormone replacement therapy allowed

- See Disease Characteristics

- At least 3 weeks since prior radiotherapy for the malignant tumor and recovered

- No concurrent radiotherapy

- Recovered from prior recent surgery

- At least 3 weeks since any prior therapy directed at the malignant tumor

- No prior cancer treatment that would contraindicate study therapy