Oral Tamoxifen and Abemaciclib in Postoperative Therapy for Male Breast Cancer: A Case Report

BACKGROUND Abemaciclib is a selective cyclin-dependent kinase inhibitor that has been approved as an adjuvant treatment for advanced hormone-positive, human epidermal growth factor receptor-2 (HER2)-negative breast cancer and is usually used in combination with an aromatase inhibitor. This report describes the case of a 43-year-old man with a grade 2, stage IIIc, hormone receptor-positive, HER2-negative, invasive ductal carcinoma of the left breast successfully managed with left mastectomy, radiation therapy, and postoperative oral tamoxifen and abemaciclib. CASE REPORT A 43-year-old man presented to our Dermatology Department with a primary concern of non-healing erosion in the left areola that persisted despite 3 months of topical ointment application. Tissue diagnosis confirmed breast cancer, and the patient was referred to the Breast Surgery Department. Imaging studies and detailed tissue analysis revealed a grade 2, hormone receptor-positive, HER2-negative, invasive ductal carcinoma of the left breast. The preoperative stage was cT4bN1aM0 (tumor with skin involvement, limited axillary node metastases, no distant spread), corresponding to stage IIIB. The patient underwent surgery (left mastectomy with axillary lymph node dissection; levels I-III). The pathological stage was IIIC (pT4bN3aM0: skin involvement with extensive nodal metastases and no distant disease). We administered postoperative adjuvant chemotherapy with sequential administration of anthracycline and taxane, and postoperative radiation therapy, followed by postoperative adjuvant endocrine therapy with tamoxifen and abemaciclib. To date, no signs of recurrence have been observed. CONCLUSIONS This report describes a rare case of advanced male breast cancer and a successful outcome following postoperative treatment that included abemaciclib.