Inclusion Criteria:

          -  PRE-REGISTRATION: Clinical T1-3, N0-3 breast cancer at diagnosis (prior to the start
             of neoadjuvant chemotherapy) by American Joint Committee on Cancer (AJCC) staging
             version 8. Note: Benign breast disease, lobular carcinoma in situ (LCIS) or ductal
             carcinoma in situ (DCIS) in the contralateral breast is allowed. Contralateral
             invasive breast cancer is allowed if disease is of clinically lower stage and the
             higher stage lesion will be the study lesion for all biopsies and tissue samples.

          -  PRE-REGISTRATION: Histological confirmation of triple negative invasive breast cancer
             (defined as estrogen receptor [ER] =< 10%, progesterone receptor [PR] =< 10% and HER2
             not amplified by in situ hybridization [ISH] or immunohistochemistry [IHC] 0/1) at
             diagnosis.

          -  PRE-REGISTRATION: Neoadjuvant chemotherapy (NAC) with one of the following regimens
             that was not discontinued early due to intolerability with less than 50% of planned
             treatment given due to disease progression or patient request:

               -  Paclitaxel or docetaxel followed by one of the following: the combination of
                  doxorubicin and cyclophosphamide (AC); the combination of epirubicin and
                  cyclophosphamide (EC) or the combination of 5-fluorouracil, epirubicin and
                  cyclophosphamide (FEC)

                    -  Note: Carboplatin may be added to these regimens

               -  AC or EC or FEC followed by docetaxel or paclitaxel

                    -  Note: Carboplatin may be added to these regimens

               -  Docetaxel in combination with doxorubicin and cyclophosphamide (TAC)

          -  PRE-REGISTRATION: Residual lesion/enhancement seen in the breast on breast imaging
             performed after completion of NAC.

          -  PRE-REGISTRATION: Able to swallow oral medication.

          -  PRE-REGISTRATION: Willing to undergo biopsy for research.

          -  PRE-REGISTRATION: Willing to provide tissue and blood samples for correlative research
             purposes.

          -  PRE-REGISTRATION: Willing to stop use of strong and moderate inducers and/or strong
             inhibitors of cytochrome P450 3A =< 7 days prior to registration.

          -  PRE-REGISTRATION: Provide written informed consent.

          -  REGISTRATION: Registration must occur =< 56 days after last dose of NAC.

          -  REGISTRATION: Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1,
             or 2.

          -  REGISTRATION: Absolute neutrophil count (ANC) >= 1500/mm^3 (obtained after completion
             of NAC but =< 14 days prior to registration).

          -  REGISTRATION: Platelets (PLT) >= 100,000/mm^3 (obtained after completion of NAC but =<
             14 days prior to registration).

          -  REGISTRATION: Hemoglobin (HgB) >= 8.0 g/dL (obtained after completion of NAC but =< 14
             days prior to registration).

          -  REGISTRATION: Total bilirubin =< 1.5 x upper limit of normal (ULN) (obtained after
             completion of NAC but =< 14 days prior to registration).

          -  REGISTRATION: Aspartate transaminase (AST) serum glutamic oxaloacetic transaminase
             (SGOT) =< 3 x ULN (obtained after completion of NAC but =< 14 days prior to
             registration).

          -  REGISTRATION: Alanine transaminase (ALT) serum glutamate pyruvate transaminase (SGPT)
             =< 3 x ULN (obtained after completion of NAC but =< 14 days prior to registration).

          -  REGISTRATION: Serum creatinine =< 1.5 x ULN (obtained after completion of NAC but =<
             14 days prior to registration).

          -  REGISTRATION: Negative pregnancy test done =< 7 days prior to registration, for
             persons of childbearing potential only.

        Exclusion Criteria:

          -  PRE-REGISTRATION: History of deep venous thrombosis (DVT) or pulmonary embolisms (PE)
             =< 12 months prior to preregistration; OR Active DVT and/or PE requiring
             anti-coagulant therapy.

               -  NOTE: Patients who are on anti-coagulant therapy for maintenance are eligible as
                  long as the DVT and/or PE was > 12 months prior to enrollment and there is no
                  evidence for active thrombosis (either DVT or PE).

               -  NOTE: Patients on anticoagulation are eligible; however peri-biopsy and
                  peri-surgical management of anticoagulation is per the institutional standard of
                  care.

          -  PRE-REGISTRATION: Prior treatment with CDK 4/6 inhibitors (e.g. palbociclib,
             ribociclib, abemaciclib, etc.)

          -  PRE-REGISTRATION: Prior treatment with immunotherapy or radiation for this breast
             cancer.

          -  PRE-REGISTRATION: Prior incisional or excisional breast biopsy for this cancer.

          -  PRE-REGISTRATION: Any contraindications to pre-registration biopsy (such as bleeding
             diatheses, etc.).

          -  PRE-REGISTRATION: Receiving any investigational agent which would be considered as a
             treatment for the primary neoplasm.

          -  PRE-REGISTRATION: Other active malignancy =< 5 years prior to registration.

               -  EXCEPTIONS: Non-melanotic skin cancer or carcinoma-in-situ of the cervix.

               -  NOTE: If there is a history of prior malignancy, they must not be receiving
                  another specific treatment for prior malignancy.

          -  PRE-REGISTRATION: Biopsy proven stage IV disease.

          -  PRE-REGISTRATION: Serious pre-existing medical conditions that would preclude
             participation in this study (for example, interstitial lung disease, severe dyspnea at
             rest or requiring oxygen therapy, history of major surgical resection involving the
             stomach or small bowel, or preexisting Crohn?s disease or ulcerative colitis or a
             preexisting chronic condition resulting in baseline grade 2 or higher diarrhea).

          -  PRE-REGISTRATION: History of any of the following conditions:

               -  Syncope of cardiovascular etiology.

               -  Ventricular arrhythmia of pathological origin (including, but not limited to,
                  ventricular tachycardia and ventricular fibrillation).

               -  Sudden cardiac arrest.

               -  NOTE: Patients on anticoagulation are eligible; however peri-biopsy and
                  peri-surgical management of anticoagulation is per the institutional standard of
                  care.

          -  REGISTRATION: Any of the following because this study involves an investigational
             agent whose genotoxic, mutagenic and teratogenic effects on the developing fetus and
             newborn are unknown:

               -  Pregnant persons.

               -  Nursing persons.

               -  Persons of childbearing potential who are unwilling to employ adequate
                  contraception.

          -  REGISTRATION: Failure to recover to grade 1 or lower from effects of chemotherapy

               -  Exceptions: Residual alopecia and grade 2 peripheral neuropathy are allowed.

          -  REGISTRATION: Concurrent use of strong and moderate inducers and/or strong inhibitors
             of cytochrome P450 3A =< 7 days prior to registration.

          -  REGISTRATION: Known infections as follows (NOTE: Screening is not required for
             enrollment):

               -  Active bacterial infection requiring intravenous antibiotics.

               -  Active fungal infection (requiring intravenous or oral antifungal treatment).

               -  Detectable viral infections (e.g. known human immunodeficiency virus [HIV], known
                  active hepatitis B or C).