The disease is more common in young women, with 18-25 years being the most common age range. Tumors mostly occur on one side of the breast, are usually single and most commonly found in the upper outer quadrant of the breast. The lumps are usually round or oval in shape, with varying sizes and hardness. They have a smooth surface, clear boundaries, high mobility, do not adhere to surrounding tissues, and are not associated with pain or tenderness. They grow slowly and do not develop into abscesses. They are not related to the menstrual cycle. Mo-targeted X-ray imaging and other imaging exams can aid in diagnosis. If necessary, fine needle aspiration cytology or biopsy may be performed to confirm the diagnosis.

Traditional Chinese medicine refers to fibrocystic disease of the breast as "breast nucleus" and it has also been referred to as "breast tumor" in some traditional Chinese medicine books. To avoid confusion in naming, it has been standardized as the category of "breast nucleus". According to "Surgery Grand Mastery", a small percentage of breast nuclei may gradually evolve into breast tumors over a long period of time.

While breast cancer poses a life-threatening situation for women, benign breast tumors also cause indescribable pain. Among them, fibroadenoma is the most common, accounting for 3/4 of all benign tumors. Fibroadenomas are usually single, round or oval in shape, with a smooth surface and clear borders. They can be easily moved and are not adherent to the skin or deep tissues. Most fibroadenomas grow slowly and are painless or only cause mild dull pain. Patients may not feel anything in their daily lives. Due to the lack of a relationship between fibroadenoma pain and the menstrual cycle, it is easy to distinguish it from breast hyperplasia.

The clinical symptoms of fibroadenoma can be categorized into three types:

1. Common type: The most common type, with small and slow-growing tumors, generally less than 3cm.

2. Youthful type: This type mostly occurs at the beginning of the menstrual cycle, with the characteristic of rapid growth and larger tumor size, reaching up to 1-13cm in about one year.

3. Giant fibroadenoma: More common in middle-aged women, especially during pregnancy, lactation, or premenopause, with larger growth, reaching more than 10cm, and possibly sarcomatous transformation.

The formation of fibroadenoma is related to the vigorous function of the ovaries, the sensitivity of the body and local breast tissue to excessive estrogen stimulation. The initial tumor is small, grows slowly, is usually 1-3cm in size, often symptomless, and rarely causes pain or tenderness. It is often discovered incidentally, mostly during showers, and can be single or multiple. The tumor appears round or oval, nodular or lobulated in shape, with a smooth surface, solid texture, clear boundaries, no adhesion to surrounding tissues, and a sliding sensation upon touch, with no changes in the appearance of the skin and no enlargement of the axillary lymph nodes.

Fibroadenoma patients may present with:

- A bright clear discharge from the nipple, but this is rare, accounting for about 0.75%.

- Pain: Mostly painless, with only 14% experiencing mild pain, which can be intermittent, occasional, or provoked by the menstrual cycle.

- A lump: Mostly discovered incidentally. 2/3 of the lumps are between 1cm-3cm in size, occasionally reaching 10cm or more. Most are single, with a round or oval shape, clear borders, smooth surface, firm texture, good mobility, and no adhesion to the skin and chest muscles.

Fibroadenoma is a mixed tumor that occurs in the fibrous tissue and glandular epithelium of the breast lobules, making it the most common benign tumor of the breast. It can occur in women of any age after adolescence, but is most common in young women aged 18 to 25. The occurrence of fibroadenoma is related to imbalances in endocrine hormones, such as relative or absolute elevation of estrogen levels. The main symptom is painless breast lump, rarely accompanied by breast pain and nipple discharge. As for whether fibroadenoma will undergo malignant transformation, it is generally believed that a small percentage of fibroadenoma cases can undergo fibrous sarcomatous transformation, with very few cases undergoing epithelial carcinoma transformation.