ABSTRACT Neuroendocrine
breast cancer (NEBC) is a rare and heterogeneous entity. It most commonly presents a
luminal phenotype and a worse
prognosis. When diagnosed in an advanced stage,
metastasis from another
neuroendocrine tumor should be excluded. This case features a premenopausal
woman with an oligometastatic
breast large
cell neuroendocrine carcinoma,
estrogen receptor (ER) positive, and
human epidermal growth factor receptor 2 (HER2) negative. Since the
patient was very symptomatic at the presentation of the
disease,
chemotherapy was started. Complete radiological response of the metastatic
disease was achieved, and the
patient was then submitted to radical
breast surgery and bilateral
oophorectomy. She subsequently underwent
radiation therapy. Since then and to date, she has been under endocrine
therapy (ET) and a CDK4/6 inhibitor (CDK4/6i), with no evidence of malignant
disease. Evidence to guide the choice of
treatment for these
tumors is currently scarce. In cases with oligometastatic
disease, radical
treatment should be considered. Given that this entity is rare, its
reporting should be encouraged.