The tumor must have estrogen receptor (ER)-and progesterone receptor (PgR)-status assessed using current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines; patients are eligible if the tumor staining meets one of the following criteria:\r\n* ER-negative and PgR- negative by ASCO/CAP guidelines, OR\r\n* ER or PgR stains are positive in -% of cells and neither is positive in >= % of cells
Patients must have had estrogen receptor (ER) analysis performed on the primary breast tumor before neoadjuvant therapy according to current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guideline recommendations for hormone receptor testing; if negative for ER, assessment of progesterone receptor (PgR) must also be performed according to current ASCO/CAP guideline recommendations for hormone receptor testing
Patients must have histologically confirmed estrogen receptor (ER)-, progesterone receptor (PR)- and HER-negative (triple-negative, TNBC) or ER, PR, and HER equivocal status and must not have received and not be planning to receive adjuvant anti-HER or endocrine therapies after completion of neoadjuvant chemotherapy; patients who are HER positive by American Society of Clinical Oncology (ASCO) College of American Pathologists (CAP) guidelines are ineligible; HER negative and HER equivocal cases as per ASCO CAP guidelines that do not receive HER-targeted therapy are eligible; patients with weekly ER or PR positive disease, defined as ER and/or PR < % by immunohistochemistry, are eligible if the treating physician considers the patient not eligible for adjuvant endocrine therapy; residual disease must be >=  cm in greatest dimension, and/or have positive lymph nodes (ypN+) observed on pathologic exam\r\n* NOTE: Immunohistochemistry (IHC)-positive isolated tumor cells in the lymph node (N [i+]) are not considered node-positive and these patients also must have >=  cm residual invasive cancer in the breast in order to be eligible
Cohort B Safety Run-In (Ribociclib + PDR + Fulvestrant): Hormone receptor (HR)-positive, HER-negative metastatic breast cancer according to ASCO CAP guidelines
Expansion Cohort B (Ribociclib + PDR + Fulvestrant): Hormone receptor (HR)-positive, HER-negative metastatic breast cancer according to ASCO CAP guidelines
Either the primary tumor and/or the metastasis must have been tested for estrogen receptor (ER), progesterone receptor (PR) and HER; patient must have HER+ breast cancer per American Society of Clinical Oncology (ASCO) College of American Pathologists (CAP) guidelines 
Breast cancer must be estrogen receptor (ER)-negative, and HER- negative according to College of American Pathologists (CAP)/American Society of Clinical Oncology (ASCO) biomarkers testing guidelines; tumors may be progesterone receptor (PgR) positive with an Allred score of less than 
Histologically or cytologically confirmed invasive breast cancer of the following subtype:\r\n* TRIPLE NEGATIVE (estrogen receptor [ER]-negative, progesterone receptor [PR]-negative, and HER-negative disease); triple-negative patients will be defined per American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines\r\n* HER-POSITIVE: HER-positive patients will be defined per ASCO-CAP guidelines\r\n* HORMONE REFRACTORY: patients with ER/PR-positive disease according to ASCO-CAP guidelines above may be considered if they have disease progression after two lines of hormonal therapy (administered in the adjuvant or metastatic setting), or are deemed clinically hormone-resistant taking into consideration the rate of progression of disease or a short interval of time on first line hormonal therapy before progression; clinically hormone resistant patients MUST also be discussed with the Study Chair, Study co-Chair (Roisin Connolly, MBBCh), or designee in advance for approval\r\n** NOTE: ASCO-CAP guidelines state that ER and PR assays be considered positive if there are at least % positive tumor nuclei in the sample on testing in the presence of expected reactivity of internal (normal epithelial elements) and external controls; HER-positive is defined as HER immunohistochemistry (IHC) +, in situ hybridization (ISH) >= ., or average HER copy number >= . signals\r\n** NOTE: a patient who has a change in receptor status (e.g. PR negative to positive) may be stratified as triple negative or hormone positive, contrary to the most recent receptor testing, for the purposes of the study, based upon the clinical course at the discretion of the Study Chair, Study co-Chair (Roisin Connolly, MBBCh), or designee in advance for approval
Hormone receptor (HR) status of the invasive component must be documented before trial enrollment; the tumor must be HR-positive; HR will be considered positive if staining is % or greater for ER and/or PR; this will be determined at the enrolling institution for purposes of study participation and enrollment onto the trial; subsequently, HR status will be confirmed by central pathology review, but this central review will not be required prior to enrolling the patient; HER status will be determined locally only, based upon current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines
Either the primary tumor and/or metastatic tumor must be triple-negative as defined below:\r\n* Hormone receptor status: the invasive tumor must be estrogen receptor (ER)- and progesterone receptor (PR)-negative, or staining present in < % by immunohistochemistry (IHC)\r\n* HER status: the invasive tumor must be human epidermal growth factor receptor  negative (HER-negative) by the American Society of Clinical Oncology College of American Pathologists (ASCO CAP) guidelines\r\n* Note: In cases where both primary tumor and metastatic sample(s) have been tested for ER, PR, and HER, the triple-negative status of the most recent sample should be used
Histopathological diagnosis of metastatic or inoperable locally advanced triple negative breast cancer (TNBC) that meets the following criteria:\r\n* Triple negative is generally defined as estrogen receptor (ER) < %, progesterone receptor (PR) < %, and HER negative according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines by local testing according to institutional standards\r\n** Note: for tumors with equivocal interpretation of receptor status (e.g., ER/PR >= % weak or faint staining), the principal investigator will have final determination of triple-negative status; for tumors with discrepant receptor results between  or more biopsies (including metastatic and/or early stage biopsies), the principal investigator will have final determination of triple negative status, but in general the most recent biopsy can be used for eligibility purposes; if receptor testing is not available on a metastatic biopsy, the primary tumor test result is acceptable\r\n* Metastatic or inoperable locally advanced disease is defined as either: histologically confirmed metastatic breast cancer by biopsy; or locally advanced breast cancer that, in the opinion of the treating physician, is not amenable to curative intent surgical resection; or, radiological or clinical evidence suggestive and supportive of metastatic disease without a documented metastatic biopsy, provided the patient has a prior diagnosis of TNBC that otherwise meets the eligibility criteria\r\n* Ductal, lobular, mixed, or metaplastic histology
Invasive disease must have been tested for estrogen receptor (ER), progesterone receptor (PR) and HER; participants must have hormone-receptor positive, HER-negative breast cancer defined as:\r\n* ER > % or PR > %\r\n* HER-negative per American Society of Clinical Oncology (ASCO) College of American Pathologist (CAP) guidelines, 
Invasive disease must have been tested for estrogen receptor (ER), progesterone receptor (PR), and HER and participants must have hormone receptor-positive, HER-negative breast cancer (ER > % or PR > %, AND HER-negative per American Society of Clinical Oncology [ASCO] College of American Pathologists [CAP] guidelines, )
Histologically confirmed metastatic triple negative breast cancer with measurable disease by RECIST . criteria hormone receptor (HR) defined as positive for the purposes of this study, if expression of estrogen receptor (ER) and/or progesterone receptor (PR) expression is greater than % by immunohistochemistry (IHC) and HER negative or non-amplified is determined by the current American Society of Clinical Oncology-College of American Pathologists (ASCO-CAP) criteria, which are as follows: HER testing by IHC as  or +. If HER is +, ISH (in situ hybridization) must be performed.
Tumor must be estrogen receptor and/or progesterone receptor positive (i.e hormone receptor positive [HR+] and HER- negative as defined by the American Society of Clinical Oncology/College of American Pathologists [ASCO-CAP] guidelines: HR+ is defined as expression of ER and/progesterone receptor [PR] in >= % of cells, or HR+ by local laboratory or regional definition; HER? is defined as a HER immunohistochemistry [IHC] score of  or +, or an IHC score of + accompanied by a negative fluorescence, chromogenic, or silver in situ hybridization test indicating the absence of HER gene amplification, or a HER/CEP ratio of < ., or local clinical guidelines
Estrogen-receptor and progesterone-receptor expression both < % by immunohistochemistry (IHC) and HER negative by IHC or non-amplified as determined by the current American Society of Clinical Oncology/College of American Pathologists (ASCO-CAP) criteria; if patient has more than one histological result, the most recent one has to be considered for inclusion
Have diagnosis of triple negative breast cancer (defined as estrogen receptor [ER] < % by immunohistochemistry [IHC], progesterone receptor [PR] < % by IHC, Her  negative by  American Society of Clinical Oncology [ASCO] College of American Pathologists [CAP] guidelines)
Patients must have either:\r\n*Hormone receptor (HR) negative and HER- negative (TNBC) metastatic breast cancer and have not received prior chemotherapy for metastatic disease and should have been exposed to anthracyclines and taxane in neoadjuvant and adjuvant settings (first-line); demonstrated HER- negative MBC ( or + by immunohistochemistry [IHC] or non-amplified by fluorescence in situ hybridization [FISH]) according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAPA) guidelines; Or\r\n* Histologically or cytologically confirmed estrogen receptor (ER) positive and HER- negative metastatic breast cancer are eligible if they have progressed on single agent or combination endocrine therapy (e.g. AI/palbociclib or everolimus) indicating an endocrine-refractory disease
Either the primary tumor and/or metastatic tumor must be triple-negative as defined below:\r\n* Hormone receptor status: the invasive tumor must be estrogen receptor (ER)- and progesterone receptor (PR) negative, or staining present in < % by immunohistochemistry (IHC)\r\n* HER status: the invasive tumor must be human epidermal growth factor receptor  negative (HER-negative) by the American Society of Clinical Oncology (ASCO) College of American Pathologists (CAP) guidelines\r\n* In cases where both primary tumor and metastatic sample(s) have been tested for ER, PR, and HER, then the triple-negative status of the tumor should be determined from the most recent sample available
Qualifying risk status, at diagnosis utilizing receptor testing by American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines, meeting one of the following:\r\n* Histologically positive axillary lymph nodes\r\n* Primary tumor that is estrogen receptor (ER)/progesterone receptor (PR)/Her negative\r\n* Primary tumor that is ER+/Her negative/lymph node negative with Breast Cancer Recurrence Score of >=  per the Genomic Health Oncotype diagnosis (DX) breast cancer test\r\n* Evidence of residual disease in the breast on pathological assessment after neoadjuvant chemotherapy
Patients must have histologically confirmed hormone receptor positive (ER and/or progesterone receptor [PR]), human epidermal growth factor receptor  (HER) negative, early invasive breast cancer; ER, PR and HER measurements should be performed according to institutional guidelines, in a Clinical Laboratory Improvement Amendments (CLIA)-approved setting in the United States (US) or certified laboratories for non-US regions; cut-off values for positive/negative staining should be in accordance with current ASCO/CAP (American Society of Clinical Oncology/College of American Pathologists) guidelines; central confirmation is not required for ER, PR, or HER statuses
Most recent tumor biopsy or surgical resection specimen must be either estrogen receptor (ER) positive, progesterone receptor (PgR) positive, or both, as defined by immunohistochemistry (IHC) >= % (as per the American Society of Clinical Oncology-College of American Pathologists [ASCO-CAP] guidelines)
Express at least  of the hormone receptors [HR; estrogen receptor (ER) or progesterone receptor (PR)] by immunohistochemistry (IHC) to fulfill the requirement for HR+ disease on the primary tumor or metastatic lesion of the breast cancer. ER and PR assays are considered positive if there is at least % positive tumor nuclei in their sample as defined in the relevant American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) or local guidelines.
Have histologically confirmed adenocarcinoma of the breast that is either TNBC or HR positive/HER- negative; TNBC is defined as: estrogen receptor (ER)/progesterone receptor (PR) < % and HER- negative disease (Immunohistochemistry [IHC] -+ or + with HER/ ratio on Fluorescence In Situ Hybridization [FISH] =< .) according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines; HR positive is defined as: ER/PR >= % and HER- negative as per ASCO/CAP guidelines
Documentation of the following receptors based on local testing from most recent assessment:\r\n* ER-positive and/or PR-positive tumor (>= % positive stained cells)\r\n* HER-negative tumor; NOTE: HER-negative is determined as immunohistochemistry score /+ or negative by in situ hybridization (FISH/CISH/SISH) defined as a HER/CEP ratio < , for single probe assessment a HER copy number <  or per current American Society Clinical Oncologists (ASCO)-College of American Pathologists (CAP) or National Comprehensive Cancer Network (NCCN) guidelines
Histologically confirmed metastatic or recurrent triple-negative (i.e. estrogen receptor =< %, progesterone receptor =< %, HER-negative via immunohistochemistry [IHC] or fluorescent in situ hybridization [FISH] per American Society of Clinical Oncology [ASCO]/College of American Pathologists [CAP] guidelines ) breast cancer
A diagnosis of invasive breast cancer, with or without an in situ component, that is: \r\n* Originally identified by screening mammography \r\n* Characterized by standard diagnostic mammography +/- breast ultrasound\r\n* Clinically node negative \r\n* Confirmed by breast magnetic resonance imaging (MRI) in a facility that maintains active American College of Radiology (ACR) accreditation to be of low clinical stage (=<  cm, node negative, unifocal invasive)\r\n* Estrogen receptor (ER) and progesterone receptor (PR) Allred scored, each > /\r\n* Her negative using American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines\r\n* ki? proliferation scored, < %\r\n* Clinical Nottingham grade  or \r\n* Scored on the MammaPrint -gene breast cancer recurrence assay as low risk
Patients must have known estrogen receptor (ER), progesterone receptor (PR), and HER status defined as triple-negative breast cancer (TNBC), defined as:\r\n* ER and PR =< % by immunohistochemistry, and HER-negative (as per American Society of Clinical Oncology [ASCO]/College of American Pathologists [CAP] guidelines, defined as immunohistochemistry [IHC]  or +, or fluorescence in situ hybridization [FISH] ratio < . or HER copy number < .)
Newly diagnosed histologically confirmed stage I-III, estrogen receptor (ER), progesterone receptor (PR) and HER negative invasive breast cancer as defined by American Society of Clinical Oncology (ASCO) College of American Pathologists (CAP) guidelines for whom systemic chemotherapy would be indicated based on physician judgment following standard National Comprehensive Cancer Network (NCCN) practice guidelines (Theriault et al, )
The subject must have histologically or cytologically confirmed metastatic estrogen-receptor positive (ER+) and/or progesterone-receptor positive (PR+) and human epidermal growth factor receptor  (HER) negative breast cancer; (stains may be performed on either primary or metastatic tumor samples, ER and PR assays will be considered positive if there are at least % positive tumor nuclei in the sample as per American Society of Clinical Oncology [ASCO]/College of American Pathologists [CAP] guidelines, HER negative as per ASCO/CAP guidelines)
Histologically confirmed TNBC, defined as negative immunohistochemical staining for estrogen and progesterone receptors (=< % of nuclei positive by immunohistochemistry [IHC]) and human epidermal growth factor receptor  (HER) negative (IHC -+ or HER-neu negative according to American Society of Clinical Oncology and the College of American Pathologists [ASCO-CAP] guideline)
The tumor must have been determined to be estrogen receptor (ER) and/or progesterone (PgR) positive assessed by current American Society of Clinical Oncology (ASCO)/College of American Pathologist (CAP) guideline recommendations for hormone receptor testing; patients with >= % ER or PgR staining by IHC are considered positive
Subjects must meet at least one of the following two criteria:\r\n* Histologically proven TNBC defined as estrogen receptor (ER) immunohistochemistry (IHC) =< %, progesterone receptor (PgR) IHC =< % and human epidermal growth factor receptor (HER)- negative disease per  American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) HER testing guidelines ( or + by IHC; and/or HER ratio < . and HER copy number <  signals/cell by fluorescence in situ hybridization [FISH])\r\n* Confirmed germline BRCA or BRCA mutation associated breast cancer regardless of the subtype of breast cancer
Estrogen-receptor and progesterone-receptor expression both =< % by immunohistochemistry (IHC), and HER-negative status as determined by the current American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines; if a patient has more than one histological result, the most recent sample will be considered for inclusion
Histologically proven diagnosis of TNBC per current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guideline;\r\n* Estrogen receptor (ER) negative (ER expression =< % positive tumor nuclei), progesterone receptor (PR) negative (PR expression =< % positive tumor nuclei) and HER negative breast cancer by IHC and /or fluorescence in situ hybridization (FISH)
HER-positive as determined using ASCO-CAP Guidelines.
Tumors must be estrogen and/or progesterone receptor positive according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP)  guidelines as either estrogen receptor (ER) or progesterone receptor (PR) >= % positive nuclear staining by immunohistochemistry; estrogen and/or progesterone receptor results by Oncotype Dx will not be accepted
Participants must have histologically confirmed hormone receptor positive (HR+) HER negative metastatic or locally recurrent unresectable invasive breast cancer; both measurable and non-measurable disease are allowed; ER, progesterone receptor (PR) and HER measurements should be performed according to institutional guidelines, in a Clinical Laboratory Improvement Act (CLIA)-approved setting; cut-off values for positive/negative staining should be in accordance with current ASCO/CAP (American Society of Clinical Oncology/College of American Pathologists) guidelines
Subjects must have a histologically confirmed diagnosis of hormone receptor (HR)+/HER+ positive locally advanced unresectable or metastatic breast cancer; estrogen or progesterone receptor positivity is defined by immunohistochemistry (IHC) according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines ; HER positivity is defined by standard of care fluorescence in situ hybridization (FISH) and/or + staining by IHC according to ASCO/CAP guidelines 
Histopathological diagnosis of triple negative breast cancer (ductal, lobular, mixed or metaplastic), defined as estrogen receptor (ER) < %, progesterone receptor (PR) < %, and human epidermal growth factor receptor  (HER) negative according to American Society of Clinical Oncology/College of American Pathologists guidelines by local testing according to institutional standards; for tumors with equivocal interpretation of receptor status (e.g. weak or faint staining), the principal investigator will have final determination of triple negative status
HER positive by  American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines (immunohistochemistry [IHC] + and/or fluorescence in situ hybridization [FISH] positive; IHC + HER patients are eligible with reflex FISH positive testing with the ratio >= .) breast cancer patients with untreated asymptomatic or minimally symptomatic brain metastasis by MRI; there is no upper or lower limit to the size or number of brain metastases
Participants must have HR positive, HER-negative breast cancer (estrogen receptor [ER] > % and/or, progesterone receptor [PR] > %, HER-negative per American Society of Clinical Oncology [ASCO] College of American Pathologists [CAP] guidelines,  resulted on the primary tumor and/or a metastatic lesion)
Dose expansion: patients must have histologically or cytologically confirmed invasive adenocarcinoma of the breast (human epidermal growth factor receptor  [HER]-negative) that is locally advanced/metastatic and has progressed despite standard therapy; at least  prior chemotherapy regimen in the metastatic setting, and two lines of hormonal therapy (administered in the adjuvant or metastatic setting) for patients with hormone receptor-positive disease; NOTE: HER-negativity will be defined per American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines; patients whose tumors have HER immunohistochemistry (IHC) +, in situ hybridization (ISH) >= ., or average HER copy number >= . signals per cell are not eligible
Participants must have biopsy proven localized estrogen receptor (ER) positive (+) (>= %), HER negative, any grade, invasive breast adenocarcinoma, with pathological stage (including post-neoadjuvant therapy) Tc-Tc, any N, M, by American Joint Committee on Cancer (AJCC) seventh (th) edition staging; invasive breast cancer must be ER+ in >= % of the cells and HER negative (immunohistochemistry [IHC]  or + and/or fluorescence in situ hybridization [FISH] negative with a ratio < ) by American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines; for IHC +, the tumor must be FISH negative with a ratio < ; progesterone receptor (PR) status must be performed; ER, PR and HER measurements should be performed according to institutional (local) guidelines, in a Clinical Laboratory Improvement Act (CLIA)-approved setting; evaluation for metastatic disease is not required in the absence of symptoms; patients must have completed definitive surgery for breast cancer
Patients must have had ER analysis performed on the primary breast tumor collected prior to neoadjuvant therapy according to current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guideline recommendations for hormone receptor testing; if negative for ER, assessment of progesterone receptor (PgR) must also be performed according to current ASCO/CAP Guideline Recommendations for hormone receptor testing
Histologically proven infiltrating carcinoma of the breast on core needle biopsy that is:\r\n* ER/progesterone receptor (PR) =< % staining by immunohistochemistry (IHC)\r\n* HER positive  IHC +, in situ hybridization (ISH) >= ., or average HER copy number >= . signals per cell or per current ASCO-CAP (American Society of Clinical Oncology  College of American Pathologists) or NCCN (National Comprehensive Cancer Network) guidelines\r\n* Note: All histological diagnostic material should be reviewed at enrolling institution as required per local standards
Histologically proven diagnosis of breast cancer with evidence of metastatic disease or locoregional recurrence. . Histological confirmation and documentation of estrogen receptor (ER)-positive status (?% positive stained cells). . Histological or cytological confirmation and documentation of human epidermal growth factor receptor- (HER)-negative status by local laboratory testing using criteria in the American Society of Oncology (ASCO)/College of American Pathologists (CAP) Clinical Practice Guideline update.