Complete Response Following Multimodal Treatment of HER2-Positive Oligometastatic Apocrine Breast Carcinoma: A Report of a Rare Case and Literature Review

Apocrine carcinoma of the breast is a rare histologic subtype characterized by distinctive morphological and immunohistochemical features. Due to its infrequent occurrence, there is a paucity of specific management guidelines, with treatment generally following the protocols applied to more common breast cancer subtypes. Here, we report the case of a 54-year-old woman with HER2-positive apocrine breast carcinoma and a solitary bone metastasis in the L5 vertebra. She received neoadjuvant chemotherapy combined with dual anti-HER2 therapy (trastuzumab and pertuzumab), followed by a right mastectomy with axillary lymph node dissection, locoregional conformal radiotherapy, and stereotactic radiotherapy to the L5 lesion. The patient then underwent adjuvant maintenance targeted therapy. A complete response, both histological and metabolic, was achieved and has been sustained after two years of follow-up. This case underscores the value of a personalized, multimodal treatment approach.