INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASHINGTON UNIVERSITY [WASH U] GENOMICS AND PATHOLOGY SERVICES [GPS] LABORATORY): Tumor tissue tested positive for HER mutation; mutations outside the list will be assessed on a case-by-case basis by the study team to determine eligibility\r\n* Note: HER mutations listed and detected by Guardant are also eligible
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Agree to provide archival tumor material for research
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): ECOG performance status =< 
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Absolute neutrophil count: >= . x ^/L (/mm^) within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Platelet count: >=  x ^/L (,/mm^) within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Serum creatinine: =< . x ULN within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Total bilirubin: =< . x ULN (in case of known Gilberts syndrome, <  x ULN is allowed) within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): AST and ALT: =<  x ULN or =<  x ULN for patients with liver metastases within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): The patient must have completed radiation therapy and be at least  week from the last systemic therapy administration, with adequate recovery of bone marrow and organ functions, before starting neratinib
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Presence of disease progression on the most recent disease evaluation
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Patients with known treated brain metastasis are eligible, but must have received radiation and be off steroids and stable (without evidence of disease progression by imaging or exam) for  months
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Corrected QT (QTc) interval =<  msec for men or =<  msec for women within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Left ventricular ejection fraction (LVEF) >= institutional lower limit of normal (LLN) within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): Able to understand and willing to sign an IRB approved written informed consent document
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED BY WASH U GPS LABORATORY): There is no limitation on the number of prior lines of systemic therapy
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLINICAL LABORATORY IMPROVEMENT ACT [CLIA] CERTIFIED LOCATION): Histologically or cytologically confirmed HER-negative ( or + by IHC or non- amplified by FISH) breast cancer that is stage IV
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Tumor tissue or circulating tumor deoxyribonucleic acid (DNA) tested positive for HER mutation; mutations outside the list will be assessed on a case-by-case basis by the study team to determine eligibility
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): ECOG performance status =< 
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Absolute neutrophil count: >= . x ^/L (/mm^) within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Platelet count: >=  x ^/L (,/mm^) within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Serum creatinine: =< . x ULN within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Total bilirubin: =< . x ULN (in case of known Gilberts syndrome, <  x ULN is allowed) within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): AST and ALT: =<  x ULN or =<  x ULN for patients with liver metastases within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): The patient must have completed radiation therapy and be at least  week from the last systemic therapy administration, with adequate recovery of bone marrow and organ functions, before starting neratinib
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Presence of disease progression on the most recent disease evaluation
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Patients with known treated brain metastasis are eligible, but must have received radiation and be off steroids and stable (without evidence of disease progression by imaging or exam) for  months
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): QTc interval =<  msec for men or =<  msec for women within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): LVEF >= institutional LLN within  weeks of registration
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): Able to understand and willing to sign an IRB approved written informed consent document
INCLUSION CRITERIA FOR REGISTRATION (HER MUTATION IDENTIFIED AT AN OUTSIDE CLIA CERTIFIED LOCATION): There is no limitation on the number of prior lines of systemic therapy