A 31-year-old woman presented to our hospital because of a lump 5cm in diameter in her right breast. Ultrasonography revealed a multilocular cystic mass with partial thickening of the wall and the septum. Core needle biopsy (CNB) of the septum confirmed invasive ductal carcinoma. The patient was administered neoadjuvant chemotherapy consisting of 12 cycles of weekly paclitaxel followed by 4 cycles of FEC (5FU, Epilubicin and cyclophosphamide). While the thickness of the wall and septum became thinner, the tumor size did not change in diameter. She underwent right mastectomy and sentinel node biopsy. Post-surgical histopathological findings showed a pathological complete response (pCR).
We report a rare case of invasive ductal carcinoma presenting a multilobular phenotype which showed pCR by neoadjuvant chemotherapy despite no size reduction of the tumor.
嚢胞内乳癌（intracystic breast cancer）