A Study Evaluating Trastuzumab Emtansine Plus Pertuzumab Compared With Chemotherapy Plus Trastuzumab and Pertuzumab for Participants With Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Breast Cancer

Inclusion Criteria:

Histologically confirmed invasive breast cancer with a primary tumor size of greater than (>) 2 cm
HER2-positive breast cancer
Participants with multifocal tumors (more than one tumor confined to the same quadrant as the primary tumor) are eligible provided all discrete lesions are sampled and centrally confirmed as HER2 positive
Stage at presentation: cT2-cT4, cN0-cN3, cM0, according to American Joint Committee on Cancer (AJCC) staging system
Known hormone receptor status of the primary tumor
Participant agreement to undergo mastectomy or breast-conserving surgery after neoadjuvant therapy
Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
Baseline Left Ventricular Ejection Fraction (LVEF) >/= 55 percent (%) measured by echocardiogram (ECHO) or multiple-gated acquisition (MUGA)
Effective contraception as defined by protocol

Exclusion Criteria:

Stage IV (metastatic) breast cancer
Participants who have received prior anti-cancer therapy for breast cancer except those participants with a history of breast lobular carcinoma in situ (LCIS) that was surgically managed or ductal carcinoma in situ (DCIS) treated exclusively with mastectomy. In case of prior history of LCIS/DCIS, >5 years must have passed from surgery until diagnosis of current breast cancer
Participants with multicentric (multiple tumors involving more than 1 quadrant) or bilateral breast cancer
Participants who have undergone incisional and/or excisional biopsy of primary tumor and/or axillary lymph nodes
Axillary lymph node dissection or positive sentinel lymph node prior to start of neoadjuvant therapy
History of concurrent or previously non-breast malignancies except for appropriately treated (1) non-melanoma skin cancer and (2) in situ carcinomas, including cervix, colon, and skin. A participant with previous invasive non-breast cancer is eligible provided he/she has been disease-free >/= 5 years
Treatment with any investigational drug within 28 days prior to randomization
Current National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) version (v) 4.0
Any significant concurrent medical or surgical conditions or findings that would jeopardize the participant's safety or ability to complete the study
Current pregnancy or breastfeeding