Primary Objective: To assess the activity of Afatinib in patients with persistent or recurrent uterine serous carcinoma overexpressing HER2/neu with the frequency of patients who survive progression-free for at least 6 months after initiating therapy. Secondary Objectives: To assess objective response rate and durable disease control rate. To assess overall survival. To assess the safety profile of Afatinib in uterine serous carcinoma patients.

Exploratory/correlative objectives: To systematically evaluate HER2/neu expression/amplification using standardized scoring criteria for both breast and gastric cancer and correlate clinical response in uterine serous carcinoma patients with HER2/neu scoring results. To correlate objective response rate, PFS and overall survival with the presence/absence of phosphatidyl inositol 3-kinase catalytic subunit and F-box/WD repeat-containing protein mutations by standard Sanger sequencing, and presence/absence of Cyclin E2 overexpression by IHC in endometrial cancer patients overexpressing HER2/neu treated with Afatinib. To study HER2/neu extracellular domain circulating levels in the plasma of uterine serous carcinoma patients overexpressing HER2/neu before and during Afatinib treatment to elucidate whether changes in HER2/neu extracellular domain would predict response to Afatinib and to determine peripheral blood natural killer cell numbers and activity in HER2/neu+ uterine serous carcinoma patients before and during Afatinib treatment to assess the possible therapeutic contributions of immune mechanisms of action of Afatinib.

Inclusion Criteria:

• Patients must have persistent or recurrent histologically confirmed uterine serous carcinoma, harbor a tumor HER2/neu+ based upon IHC staining score of 3+ or 2+ with confirmed gene amplification by FISH.
• Have measurable disease.
• Have at least one target lesion to be used to assess response as defined by RECIST v1.1.
• After undergoing surgery may be optimally or sub optimally debulked, with measurable recurrent disease of any previous substage.
• Diagnosis histologically confirmed by a gynecologic pathologist as containing >10% uterine papillary serous adenocarcinoma in the specimen.
• Have adequate bone marrow function.
• WBC greater than or equal to 3,000/ul, platelets greater than or equal to 75,000/ul, neutrophils greater than or equal to 1500/ul., creatinine less than or equal to 2.0 mg/kl, bilirubin < 1.5 X laboratory normal, SGOT/SGPT <3 X laboratory normal.
• Have an ECOG performance status of 0 or 1.
• Have signed an approved consent.
• Have recovered from effects of recent surgery, radiotherapy or chemotherapy. Should be free of significant infection.
• Patients with recurrent disease may have received multiple prior chemotherapies for treatment of their uterine cancer.
• May have received prior trastuzumab therapy alone or in combination with chemotherapy with 2 week washout period required between trastuzumab treatment and first dose of Afatanib.
• Patients of childbearing potential must have a negative serum pregnancy test within 7 days prior to the study entry and be practicing an effective form of contraception.
• Must be 18 years of age.
• Patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial. NOTE: Patients with prior anthracycline exposure are NOT eligible.

Exclusion Criteria:

• Patients who have a significant history of cardiac disease, uncontrolled hypertension, unstable angina, uncontrolled congestive heart failure, or uncontrolled arrhythmias within 6 months of registration. Patients with any unstable medical issue, active treatment for symptomatic pulmonary embolism, CVA, renal or hepatic insufficiency, active infection/sepsis requiring IV antibiotics, known brain/leptomengial involvement of the disease, active neurological disease, dementia.
• Patients who have received prior therapy with any irreversible human epidermal growth factor receptor tyrosine kinase inhibitor.
• Patients who have an uncontrolled seizure disorder or active neurological disease. Patients known to be seropositive for HIV and active hepatitis, even if liver function studies are in the eligible range. Known hemorrhagic diathesis or active bleeding disorder.