Vitiligo-like lesions associated with ribociclib in a woman with metastatic breast cancer.

Cyclin-dependent kinase 4/6 inhibitors are new generation drugs that have recently been used in patients with hormone receptor-positive and human epidermal growth factor receptor 2-negativenegative metastatic breast cancer. Recent studies have shown that the use of cyclin-dependent kinase 4/6 inhibitors significantly improves the outcomes of these patients. The most common side effects of cyclin-dependent kinase 4/6 inhibitors are hematological toxicity, gastrointestinal side effects, and fatigue. We aimed to present a case of metastatic breast cancer who was treated with ribociclib and developed vitiligo-like lesions after treatment.A 56-year-old female patient was diagnosed with locally advanced hormone receptor (+)/human epidermal growth factor receptor 2 (-) breast cancer in May 2000. She was followed up with hormonal therapy after adjuvant chemotherapy and radiotherapy. The patient progressed with lung metastases in 2012. Ribociclib, anastrozole, and leuprolide acetate were started in November 2021 after multiple-line chemotherapy. After six cycles of ribociclib, vitiligo-like lesions that developed in the last 1 month were detected on the upper extremities, both hands, neck, chest, and upper back.The patient was referred to dermatology. Topical immunosuppressive therapy and oral corticosteroids were recommended. At the first and third-month follow-up examinations, vitiligo-like lesions were observed to persist.Vitiligo-like lesions are not a life-threatening side effect. However, it significantly affects the quality of life and disrupts the patient's compliance with treatment. Cyclin-dependent kinase  4/6 inhibitors can inhibit cell division or cause premature cell death by acting on the melanocyte cell cycle.