Case of HER2neu+ Invasive Pleomorphic Lobular Carcinoma With Response to Conventional Neoadjuvant Chemotherapy: A Viable Option for an Exceedingly Rare Breast Cancer Type.

Invasive pleomorphic lobular carcinoma (IPLC) is an extremely rare form of breast cancer that accounts for less than 1% of all breast cancer cases. Due to this rarity, currently, there is a lack of an established standard of care for patients diagnosed with this form of breast cancer. In this case report, we present a 57-year-old female with a complex oncologic history diagnosed with clinical prognostic Stage IIA (ER 5%, PR 0%, HER2neu 3+) invasive pleomorphic lobular carcinoma of the left breast treated with neoadjuvant docetaxel, carboplatin, trastuzumab, and pertuzumab-based therapy (TCHP) followed by surgery. Surgical pathology revealed treatment-related changes with a definite response to neoadjuvant therapy. We report this case to highlight the response of this rare pathological entity to a standard neoadjuvant regimen such as docetaxel, carboplatin, trastuzumab, and pertuzumab.