Trastuzumab in Treating Patients With Locally Advanced or Metastatic Synovial Sarcoma

DISEASE CHARACTERISTICS: * Histologically confirmed synovial sarcoma meeting 1 of the following stage criteria: * Locally advanced disease, defined as 1 of the following: * Incurable by conventional multidisciplinary therapy, including surgery * Surgically resectable only with significant morbidity * Metastatic disease * Tumor HER2/neu positive (2+ or 3+) by immunohistochemistry * Tumor tissue must be available AND patient must be willing to allow specimen submission * Measurable disease * No known CNS metastases PATIENT CHARACTERISTICS: Age * 18 and over Performance status * Zubrod 0-2 Life expectancy * Not specified Hematopoietic * Absolute neutrophil count \> 1,000/mm\^3 * Hemoglobin \> 8 g/dL * Platelet count \> 100,000/mm\^3 Hepatic * Bilirubin \< 1.5 times upper limit of normal (ULN) * SGOT and/or SGPT \< 1.5 times ULN (5 times ULN if liver metastases are present) Renal * Creatinine \< 1.5 times ULN OR * Creatinine clearance \> 60 mL/min Cardiovascular * LVEF \> 45% by MUGA Gastrointestinal * No active peptic ulcer disease * No active gastrointestinal bleeding * No active inflammatory bowel disease Other * Not pregnant or nursing * Fertile patients must use effective contraception * No known HIV positivity * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or adequately treated stage I or II cancer in complete remission PRIOR CONCURRENT THERAPY: Biologic therapy * No concurrent filgrastim (G-CSF) Chemotherapy * At least 3 weeks since prior chemotherapy Endocrine therapy * Not specified Radiotherapy * At least 60 days since prior radiotherapy to the target lesion\* * No concurrent radiotherapy NOTE: \*Lesion must have demonstrated disease progression after completion of therapy Surgery * At least 21 days since prior major surgery and recovered Other * At least 60 days since prior embolization or radiofrequency ablation to the target lesion\* NOTE: \*Lesion must have demonstrated disease progression after completion of therapy