If a hard lump is found under a woman’s breast, there are several conditions to be considered. 1. cystic hyperplasia of the breast caused by hyperplasia of the breast tissue or dilation of the breast ducts, the hard lump appears along with the menstrual cycle and becomes soft or even disappears after the menstrual cycle, the edge of the hard lump may be irregular and poorly mobile. 2. fibroadenoma of the breast is a relatively common condition of female breast lumps, the tumor is more mobile, mostly round or round-like, with smooth edges. The edges are smooth. The only effective treatment is surgical excision. 3. Breast cancer, with irregular edges, poor mobility and rapid growth, requires timely puncture biopsy or surgical excision. 4. Acute mastitis or lactation mastitis, with painful local inflammatory masses. The symptoms can be improved through oral antibiotic medication. Try to visit the hospital and check the specific situation in detail.