Male breast cancer is rare and few cases of breast cancer in human immunodeficiency virus (HIV)-infected patients are reported. We describe the case of breast cancer in a 65-year-old HIV-positive man who presented a nodule near the nipple of his left breast. He did not report risk factors for breast cancer, but he had liver cirrhosis. Biopsy of the lesion revealed a ductal carcinoma and he was submitted to mastectomy and axillary dissection. Staging resulted in pT1c/pN1a/M0; it was positive for the presence of oestrogen/progesterone receptors, negative for the human epidermal growth factor receptor-22. He was also treated with local radiotherapy and tamoxifen. At cancer diagnosis, he received highly active antiretroviral therapy (HAART) with undetectable HIV viral load, and his CD4+ T-cell count was 445 cells/mm(3). Patients with HIV infection have a higher cancer risk due to immunosuppression: it concerns not only malignancies related to human acquired immunodeficiency syndrome (AIDS), but also other cancers. A heightened awareness of male breast cancer by HIV specialists is needed, especially for particular risk categories, such as trans-sexuals who take oestrogen therapies, and for the presence of breast conditions, such as gynecomastia, usually considered as part of the lipodystrophy syndrome.