Rapid Response of Breast Cancer Cutaneous Metastasis to Single-Agent Palbociclib: A Case Report.

Palbociclib is a cyclin-dependent kinase (CDK) 4/6 inhibitor. Palbociclib combined with endocrine therapy has shown promising results in hormone-receptor-positive (HR+) and human epidermal growth factor receptor-negative (HER-2-) breast cancer progression. We present a case of a woman with a history of infiltrating lobular cancer of the left breast, status post modified radical mastectomy 6 years prior, presenting with nodular erythematous lesions on the left arm and back. Histopathological examination confirmed the diagnosis of recurrent metastatic breast adenocarcinoma. She had complete resolution of cutaneous metastasis with 1 cycle of Palbociclib. We believe our case is unique as the resolution of cutaneous metastasis with 1 cycle of single-agent Palbociclib is rare. Furthermore, it highlights the importance of considering cutaneous metastasis as a possibility in patients with prior history of primary internal malignancy.