Pertuzumab is a molecular-targeted drug that binds to the extracellular domain of human epidermal growth factor receptor 2 (HER2) and inhibits dimer formation. The combined use of pertuzumab and trastuzumab for HER2-positive breast cancer has been reported to significantly increase the rate of pathological complete response (pCR) compared to that with trastuzumab monotherapy. We reported the outcomes of HER2-positive breast cancer treated with neoadjuvant chemotherapy with pertuzumab. Sixteen patients with stages II–III HER2-positive breast cancer were treated with 4 cycles of docetaxel (75 mg/m2) with trastuzumab and pertuzumab, followed by 4 cycles of 5-fluorouracil (500 mg/m2), epirubicin (100 mg/m2), and cyclophosphamide (500 mg/m2). The participants were in the age range of 45–76 years; T1, T2 and T3 stages were reported in 2, 11, and 3 cases, respectively, and N0 and N1 stages were reported in 6 and 10 cases, respectively. Luminal HER2 and HER2-enriched subtypes were noted in 8 cases each. In all cases, scheduled chemotherapy was completely implemented. Grade 3, 2b, 1a and 1b histology were observed in 11, 3, 1, and 1 cases, respectively. The rate of pCR (ypT0/is + ypN0) was 69%, whereas the objective response rate was 94%. In 12 cases, breast-conserving surgery was undertaken, whereas 4 patients underwent total mastectomy. Pertuzumab did not cause any complications, including cardiac dysfunction.PertuzumabはHER2の細胞外ドメインに結合し、ダイマー形成を阻害するである。種々の試験において、trastuzumab単独よりもPertuzumabを併用した方が病理学的完全奏効率(pCR)を有意に上昇すると報告されている。今回、我々はHER2陽性乳癌に対してPertuzumabを用いた術前化学療法を行った。16名のStageII～IIIのHER2陽性乳患者に、Pertuzumab、Trastuzumab、Docetaxel（75 mg/m2）4コース、その後にFEC100療法4コースを施行した。年齢は45～76歳で、T1、T2、T3はそれぞれ2例、11例、3例、N0、N1はそれぞれ6例、10例であった。Luminal HER2 type、HER2 enrich typeともに8例であった。すべての症例で予定された化学療法が完全施行できた。組織学的効果はGrade3、2b、1a、1bがそれぞれ11例、3例、1例、1例であった。pCR（ypT0/is + ypN0）率は69％で、奏功率は94%であった。Pertuzumabによる心機能障害等の副作用は認められなかった
