Inclusion Criteria

• Documented informed consent of the participant and/or legally authorized representative
  * Assent, when appropriate, will be obtained per institutional guidelines
• Agreement to research biopsies on study, once during study and end of study, exceptions may be granted with study principal investigator (PI) approval
• >= 18 years
• Eastern Cooperative Oncology Group (ECOG) =< 2
• Histologically confirmed metastatic triple negative breast cancer. Triple negative status will be defined as estrogen receptor (ER) and progesterone receptor (PR) =< 10% by immunohistochemistry (IHC) and HER2 negative, per American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines
• Measurable disease by RECIST 1.1
• Patients must have progressed on or been intolerant of at least 2 prior lines of therapy for advanced/metastatic disease. Patients that qualify for immunotherapy and/or PARP inhibitors must have progressed on or been intolerant of these agents
• Fully recovered from the acute toxic effects (except alopecia) to =< grade 2 to prior anti-cancer therapy
• Must have a superficial tumor (cutaneous, subcutaneous), breast lesion or nodal metastases amenable to safe repeated intratumoral injections per treating physician and interventional radiologist review
• Absolute neutrophil count (ANC) >= 1,500/mm^3
  * NOTE: Growth factor is not permitted within 14 days of ANC assessment unless cytopenia is secondary to disease involvement
• Platelets >= 100,000/mm^3
  * NOTE: Platelet transfusions are not permitted within 14 days of platelet assessment unless cytopenia is secondary to disease involvement
• Total bilirubin =< 1.5 X upper limit of normal (ULN)
• Aspartate aminotransferase (AST) =< 2.5 x ULN * If liver metastases are present: AST =< 5 x ULN
• Alanine aminotransferase (ALT) =< 2.5 x ULN * If liver metastases are present: ALT =< 5 x ULN
• Serum creatinine =< 1.5 mg/dL or creatinine clearance of >= 50 mL/min per 24 hour urine test or the Cockcroft-Gault formula