Definition: It is an extremely important lesion of the breast, formed by a high degree of dilatation of the lobules, small ducts, and terminal ducts of the breast, and characterized by cysts, along with some other structural dysplasia lesions. The disease is highly prevalent and has a variety of pathological and morphological variations. The main names used are cystic mastopathy and mammary gland structural malformation. The exact pathogenesis of the disease is not well understood, but it is thought to be mainly related to ovarian endocrine dysfunction. A lot of data show that when ovarian endocrine disorders, excessive secretion of estrogen and relative decrease of progesterone not only stimulate the proliferation of breast parenchyma, but also cause irregular proliferation of terminal duct epithelium, resulting in ductal dilatation and cyst formation, and also lead to excessive proliferation and collagenization of interstitial connective tissue and lymphocyte infiltration due to the loss of the inhibitory influence of progesterone on estrogen. Although cystic hyperplasia of the breast may also extend to the large ducts, its main site of invasion is the terminal duct-lobular unit of the breast, with a high degree of variability in gross and microscopic morphology depending on which lesion predominates, with the following basic morphological changes: (1) cyst formation (2) sweat gland hyperplasia (3) fibrosis (4) calcification (5) epithelial hyperplasia (6) Inflammatory cell infiltration (7) fibroadenoma-like changes Clinical manifestations: The onset of the disease usually begins between 30-34 years of age, with a peak incidence between 40-49 years of age. The main manifestations are periodic breast pain associated with menstruation, which is aggravated in the premenstrual period and may radiate to both upper limbs. The cysts of different sizes in the breast glands are the characteristic manifestations of this disease. The cysts may be scattered in size and number, or most of them may be aggregated into a honeycomb pattern; the cyst wall is thin and smooth, with lateral acoustic shadowing, clear fluid and anechoic, with posterior echogenic enhancement. In addition, the affected side may also show localized glandular thickening, commonly in the outer upper quadrant, with a tough texture on palpation and a heterogeneous glandular echogenicity, with patchy hypoechoic or enhancing areas interspersed, and no significant changes in the distribution of blood flow within the gland. Differential diagnosis: milk retention cysts: usually seen in women who are breastfeeding or post-lactation, unilateral breasts are common, and the number is small. Fibroadenoma: with envelope, often solitary, visible as lateral acoustic shadow, mostly seen in young women, with a younger age of predilection than cystic hyperplasia of the breast. Breast cancer: very irregular in shape, fuzzy border, angular protrusion, tumor aspect ratio greater than 1, internal sand-like calcification, far-field echogenicity may be reduced, tumor often visible through the arterial blood flow.