Breast tumours. Light micrograph of a section through a human female breast, with benign (non- cancerous) tumours (neoplasms). The tumours may be fibroadenomas, the thickening of the milk- producing tissue, or fluid-filed sacs (cysts). At least 80% of breast lumps produce few symptoms and are benign. Cysts can be drained in a simple outpatient procedure, while other lumps can be removed surgically. Magnification unknown.