Me giving the presentation of our clinic case, about a male patient with breast cancer. Abstract of the case: Infiltrating ductal carcinoma complicated with malignant pleural effusion in male patient Key Words: Breast cancer, male, effusion, pleura. Abstract: The presentation of breast cancer in male humans has a very low frequency. Its incidence is less than 1% of all cases and although their natural history and histological features are similar to breast cancer in women, its epidemiology and hormonal environment are different. This study presents a 26 year-old male patient whom in 2002 presented a palpable mass in the left areolar area. With a diagnosis of infiltrating ductal carcinoma, he underwent radical mastectomy. The study of hormonal receptors reported negative estrogen and progesterone receptors. On year 2007 the patient presented progressive dyspnea, from moderate to greater efforts, concomitantly chest pain. There is evidence that chest X-ray radiopaque uniform with a density similar to the cardiac silhouette in the middle and lower thirds of left lung field, with the appearance of pleural effusion. The study of the pleural effusion liquid reported a predominance of mononuclear cells, with characteristics of exudate. Biopsy was performed pleura which is poorly differentiated carcinoma. In conclusion breast cancer in men is very rare but often very aggressive and tends to cause complications such as lung metastases that is very important for the study and control of patient.