A hard lump in a man’s breast is mainly considered to be related to abnormal development of the mammary gland, mammary cysts, r breast tumors and so on. 1. Abnormal development of mammary glands: abnormal secretion of estrogen in male body can lead to abnormal development of mammary glands, which in turn leads to the phenomenon of hard lumps in breasts. 2. Breast cysts: Usually there are no obvious discomfort symptoms, only lumps in the breast. When the cyst expands acutely, it may suddenly appear severe and limited pain. 3. Breast tumor: benign tumors such as breast fibroma and lipoma as well as malignant tumors such as breast cancer can cause breast lumps. The cause of this symptom is complex and may be related to other diseases such as pleural disease. It is recommended that patients seek medical examination as soon as possible to confirm the diagnosis of the condition, and then carry out treatment under the guidance of the doctor.