We report a case of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer with CBM….A missense mutation in PIK3CA (exon 10, c.1633G>A [p.Glu545Lys]) was detected by whole-exome next-generation sequencing from peripheral blood samples...the patient underwent fourth-line treatment with abemaciclib (100 mg bid) combined with fulvestrant (500 mg). Three months later, CBM significantly demonstrated PR and extracranial bone metastases were stable. At present, the patient has above 9 months of progression-free survival time without obvious adverse effects. This is the first report of abemaciclib combined with fulvestrant in the treatment of CBM in a patient with HR+/HER2- breast cancer.