[A Case of Multicentric HER2-Positive Breast Cancer with Alterations of the Intrinsic Subtype].

In cases where there are 2 or more tumors, it is crucial to conduct core needle biopsies on each of them. A 39-year-old woman presented at our hospital with pain in her left breast. Ultrasonography(US)revealed the presence of 2 contiguous tumors: a 35 mm tumor(tumor 1)and a 20 mm tumor(tumor 2)in the AC area of the left breast. US-guided core needle biopsies(CNB)were performed. The histological findings confirmed an invasive ductal carcinoma, characterized by ER(-)/ PR(-)/HER2(3+). Neoadjuvant chemotherapy indicated tumor 1 as PD and tumor 2 as PR, and surgery was subsequently performed(Bt plus SLN). Upon histopathological examination, the findings demonstrated a non-pCR invasive ductal carcinoma, featuring an ER(+)/PR(-)/HER2(-)profile. Depending on the specific subtype identified, post-operative treatment included HER2-targeted therapy or ER/PR-targeting hormone therapy in conjunction with chemotherapy.