It is a disease of the breast. Fibrocystic refers to a different condition and includes the old name, fibrocystic breast disease. It is the most common benign disease. Non-cancerous (non-cancerous) breast tissue forms cysts (cysts) that are smooth, firm, and motile. These changes also lead to thickening throughout the breast, pain, and soreness. The cyst may spread over one area of the breast or appear as one or more large lumps in 60% to 75% of cases. % of all women will have tissue changes in their breasts. Fibrocystic changes occur most in women aged 30 to 50. Only 10% of women under 21 are affected.