What are the common diseases associated with hypoechoic lesions in the retro-mammary space?

The breast exhibits a hypoechoic area; the most common conditions causing this finding are nodules associated with mammary cystic hyperplasia and fibroadenomas. These typically present with well-defined margins and regular morphology, and are classified as BI-RADS category 3 or lower on ultrasound. In such cases, clinical observation is appropriate, with follow-up breast ultrasound every 6–12 months. For individuals aged 40 years and older, mammography should be repeated every two years. If premenstrual breast tenderness occurs, accompanied by enlargement of the mass before menstruation and failure of the mass to shrink—or of the pain to subside—after menstruation, oral medications such as Xiao Jin Wan or Xiao Yao Wan may be prescribed for treatment.