Onset of gynecomastia in a male patient under sunitinib treatment for metastatic clear-cell renal carcinoma

Sunitinib is an orally administered multitargeted tyrosine kinase inhibitor that has demonstrated substantial antitumour activity in patients with metastatic renal cell carcinoma. The more common grade 3 or 4 adverse effects of sunitinib include hypertension, fatigue, hand-foot syndrome, elevated lipase and lymphopenia. We report the case of a 69-year-old patient with metastatic renal clear-cell carcinoma, treated with nephrectomy and three lines of therapy (interleukin-2 plus interferon-α2a, vinorelbine plus gemcitabine, and capecitabine), who started a fourth-line therapy with oral sunitinib because of disease progression. At the end of his fifth cycle of sunitinib therapy, the patient complained of the development of abnormally large mammary glands associated with pain and peri-areolar erythema. After 2 weeks off therapy, a partial reduction in mammary gland enlargement, local pain and erythema was observed. However, re-initiation of sunitinib treatment was followed by bilateral bre...