This is a phase II open-label study of the activity and safety of trastuzumab in patients with vulvar Paget's disease with overexpression of HER2 on biopsy.

The primary objective will be to estimate the anti-tumor activity of trastuzumab by evaluating the response to trastuzumab therapy in patients with recurrent or persistent vulvar Paget's disease demonstrating HER2/neu overexpression by immunohistochemistry and/ or FISH ((fluorescence in situ hybridization).

The secondary objectives:

• To evaluate the quality of life, based on the severity of the patients' vulvar itching on a 4-point verbal rating scale from 0 to 3 (0=no itching, 1=mild itching/ bothersome, 2=moderate itching/ troublesome, 3=severe itching/ extremely troublesome) as well as on the severity of the patients' vulvar pain on a numeric pain scale from 0-10 (0=no pain, 1-3=mild pain, 4-6=moderate pain, 7-10=severe pain).
• To assess the frequency and severity of observed adverse effects
• To assess the frequency/ incidence of HER2 in Paget's disease of the vulva

Inclusion Criteria:

• recurrent or persistent vulvar Paget's disease with overexpression of HER2 by immunohistochemistry and or fluorescence in situ hybridization (FISH)
• Biopsy for histologic confirmation
• Measurable disease
• Karnofsky score of 50-100
• recovered from effects of recent surgery, radiotherapy, or chemotherapy
• free of active infection requiring antibiotics
• adequate bone marrow function,renal function,hepatic function,cardiac function,WOCBP-neg.serum pregnancy,meet requirements in section 7.0

Exclusion Criteria:

• no measurable disease
• tumors not HER2 positive by immunohistochemistry FISH
• prior therapy with any anti-HER2 monoclonal antibody preparation
• Karnofsky score of 0-40
• other invasive malignancies, with the exception of non-melanoma skin cancer
• Patients requiring supplemental oxygen
• unstable medical conditions in the opinion of the treating physician place them at unacceptably increased risk from trastuzumab therapy
• Patients with active or unstable cardiac disease, or myocardial infarction within 6 months