Cystic solid breast nodules with ductal dilatation may be caused by cystic hyperplasia of the breast, changes in hormone levels in the body, and blockage of the breast ducts. 1. Breast cystic hyperplasia: cystic solid breast nodules with ductal dilatation may be caused by breast cystic hyperplasia, the symptoms usually worsen before menstruation, and there will be swelling and tingling in the breast. 2. Hormonal changes: Hormonal changes in the body, such as increased prolactin and estrogen, may cause cystic breast nodules with ductal expansion. 3. Breast duct blockage: Breast duct blockage may also cause cystic solid nodules with ductal dilatation. It is common for women to accumulate breast milk during breastfeeding, and the localized pressure on the mammary glands will hinder the discharge of breast milk, and cystic solid nodules with ductal dilatation can be found during examination. When this symptom occurs, it is necessary to go to the regular hospital for timely examination and then treatment.