■ New diagnosis of DCIS without invasive breast cancer ■ Unilateral, bilateral, unifocal, or multifocal DCIS ■ A patient who has had a lumpectomy with positive margins as part of their treatment for a current DCIS diagnosis is eligible ■ No previous history of breast cancer (DCIS or invasive cancer) in either breast prior to current DCIS diagnosis ■ 40 years of age or older at the time of DCIS diagnosis ■ ECOG performance status 0 or 1 ■ No contraindication for surgery ■ Baseline imaging: ○ Unilateral DCIS: ■ Contralateral normal mammogram ≤ 6 months of registration and ipsilateral breast imaging ≤ 120 days of registration ○ Bilateral DCIS: ■ Bilateral breast imaging ≤ 120 days of registration ■ Pathological criteria: ○ ADH suspicious for DCIS ○ Any grade I or grade II DCIS ○ Absence of invasive or microinvasive breast cancer ○ Diagnosis confirmed on core needle, vacuum-assisted biopsy or surgery ≤ 120 days of registration ○ ER(+) and/or PR(+) by IHC (≥10% staining or Allred score ≥ 4) ○ HER2 0, 1+ or 2+ by IHC if HER2 testing is performed ■ Histology slides reviewed and agreement between two clinical pathologists that pathology fulfills COMET eligibility criteria ■ At least two sites of biopsy for those cases where mammographic extent of calcifications exceeds 4 cm, with second biopsy benign or both sites fulfilling pathology eligibility criteria ■ Amenable to follow-up examinations Ability to read, understand and evaluate study materials and willingness to sign a written informed consent document in Spanish or English |