Thickened breast tissue is an abnormal density detectable during self-examination or a doctor’s exam. Causes for this condition range from common benign changes in the breast to the presence of breast cancer.
Fibrocystic breast changes involve the formation of dense, fibrous tissue or fluid-filled cysts inside the breast, according to the American Cancer Society (ACS). Roughly half of all women experience them at some time. While they typically present little danger, some cases may indicate an increased risk for breast cancer.
Benign tumours called fibroadenomas may create areas of breast tissue that feel like marbles, according to the ACS. Depending on a tumour's rate of growth, doctors may recommend surgically removing it.
Phyllodes tumours form from glandular and connective tissue in the breast, and typically manifest as a painless lump. While most cases are benign, a small number indicate the presence of cancer, according to the ACS.
The Merck Manual of Health and Aging notes that thickening of the breast may mark the onset of breast cancer. In some cases, the breast tissue remains normal while hard lumps appear in nearby lymph nodes.
The Mayo Clinic notes that the presence of fibrocystic changes may increase the difficulty of breast self-examinations.