When gigantomastia occurs in young women during puberty, the medical condition is known as "juvenile macromastia" or "juvenile gigantomastia" and sometimes as "virginal breast hypertrophy" or "virginal mammary hypertrophy". Along with the excessive breast size, other symptoms include red, itchy lesions and pain in the breasts. A diagnosis is made when an adolescent's breasts grow rapidly and achieve great weight usually soon after her first menstrual period. Some doctors suggest that the rapid breast development occurs before the onset of menstruation.

Some women with virginal breast hypertrophy experience breast growth at a steady rate for several years, after which the breasts rapidly develop exceeding normal growth. Some adolescent females experience minimal or negligible breast growth until their breasts suddenly grow very rapidly in a short period of time. This may cause considerable physical discomfort. Women suffering VBH often experience an excessive growth of their nipples as well. In severe cases of VBH, hypertrophy of the clitoris occurs.

At the onset of puberty, some females with who have experienced little or no breast development can reportedly reach three or more cup sizes within a few days (see below).

The classic feature of gynecomastia is male breast enlargement with soft, compressible, and mobile subcutaneous chest tissue palpated under the areola of the nipple in contrast to softer fatty tissue. This enlargement may occur on one side or both. Dimpling of the skin and nipple retraction are not typical features of gynecomastia. Milky discharge from the nipple is also not a typical finding, but may be seen in a gynecomastic individual with a prolactin secreting tumor. An increase in the diameter of the areola and asymmetry of chest tissue are other possible signs of gynecomastia.

Males with gynecomastia may appear anxious or stressed due to concerns about the possibility of having breast cancer.

The indication is a breast weight that exceeds approximately 3% of the total body weight. There are varying definitions of what is considered to be excessive breast tissue, that is the expected breast tissue plus extraordinary breast tissue, ranging from as little as up to with most physicians defining macromastia as excessive tissue of over . Some resources distinguish between macromastia (Greek, "macro": large, "mastos": breast), where excessive tissue is less than 2.5 kg, and gigantomastia (Greek, "gigantikos": giant), where excessive tissue is more than 2.5 kg. The enlargement can cause muscular discomfort and over-stretching of the skin envelope, which can lead in some cases to ulceration.

Hypertrophy of the breast can affect the breasts equally, but usually affects one breast more than the other, thereby causing asymmetry, when one breast is larger than the other. The condition can also individually affect the nipples and areola instead of or in addition to the entire breast. The effect can produce a minor size variation to an extremely large breast asymmetry. Breast hypertrophy is classified in one of five ways: as either pubertal (virginal hypertrophy), gestational (gravid macromastia), in adult women without any obvious cause, associated with penicillamine therapy, and associated with extreme obesity. Many definitions of macromastia and gigantomastia are based on the term of "excessive breast tissue", and are therefore somewhat arbitrary.

Symptoms: The breasts are swollen and oedematous, and the skin looks shiny and diffusely red. Usually the whole of both breasts are affected, and they are painful. The woman may have a fever that usually subsides in 24 hours. The nipples may become stretched tight and flat which makes it difficult for the baby to attach and remove the milk. The milk does not flow well.

A fever may occur in 15 percent, but is typically less than 39 degrees C and lasts for less than one day.

Breast engorgement occurs in the mammary glands due to expansion and pressure exerted by the synthesis and storage of breast milk. It is also a main factor in altering the ability of the infant to latch-on. Engorgement changes the shape and curvature of the nipple region by making the breast inflexible, flat, hard, and swollen. The nipples on an engorged breast are flat.

Engorgement usually happens when the breasts switch from colostrum to mature milk (often referred to as when the milk "comes in"). However, engorgement can also happen later if lactating women miss several nursings and not enough milk is expressed from the breasts. It can be exacerbated by insufficient breastfeeding and/or blocked milk ducts. When engorged the breasts may swell, throb, and cause mild to extreme pain.

Engorgement may lead to mastitis (inflammation of the breast) and untreated engorgement puts pressure on the milk ducts, often causing a plugged duct. The woman will often feel a lump in one part of the breast, and the skin in that area may be red and/or warm. If it continues unchecked, the plugged duct can become a breast infection, at which point she may have a fever or flu-like symptoms.

Gynecomastia is an endocrine system disorder in which there is a non-cancerous increase in the size of male breast tissue. Psychological distress may occur.

The development of gynecomastia is usually associated with benign pubertal changes. However, 75% of pubertal gynecomastia cases resolve within two years of onset without treatment. In rare cases, gynecomastia has been known to occur in association with certain disease states. The pathologic causes of gynecomastia are diverse and may include Klinefelter syndrome, certain cancers, endocrine disorders, metabolic dysfunction, various medications, or may occur due to a natural decline in testosterone production. Disturbances in the endocrine system that lead to an increase in the ratio of estrogens/androgens are thought to be responsible for the development of gynecomastia. This may occur even if the levels of estrogens and androgens are both appropriate but the ratio is altered. Diagnosis is based on signs and symptoms.

Conservative management of gynecomastia is often appropriate as the condition commonly resolves on its own. Medical treatment of gynecomastia that has persisted beyond two years is often ineffective. Medications such as aromatase inhibitors have been found to be effective in rare cases of gynecomastia from disorders such as aromatase excess syndrome or Peutz–Jeghers syndrome, but surgical removal of the excess tissue is usually required.

Gynecomastia is common. Physiologic gynecomastia develops in up to 70% of adolescent boys. Newborns and adolescent males often experience temporary gynecomastia due to the influence of maternal hormones and hormonal changes during puberty, respectively.

Witch's milk or neonatal milk is milk secreted from the breasts of some newborn human infants of either sex. Neonatal milk secretion is considered a normal physiological occurrence and no treatment or testing is necessary. It is thought to be caused by a combination of the effects of maternal hormones before birth, prolactin, and growth hormone passed through breastfeeding and the postnatal pituitary and thyroid hormone surge in the infant.

Breast milk production occurs in about 5% of newborns and can persist for two months though breast buds can persist into childhood. Witch's milk is more likely to be secreted by infants born at full term, and not by prematurely-born infants. The consistency of neonatal milk is estimated to be quite similar to maternal milk. Its production may be also be caused by certain medications. In extremely rare cases neonatal mastitis may develop but it is unclear if it is related to neonatal milk secretion.

In some cultures the tradition of removing the milk ("milking") has been reported. This practice can prolong milk production and other problems can not be excluded. While breastfeeding may also contribute to prolonged milk production and breast enlargement, temporary, or permanent weaning is not recommended.

In folklore, witch's milk was believed to be a source of nourishment for witches' familiar spirits. It was thought to be stolen from unwatched, sleeping infants. In other cultures expressing milk from the infant's breasts is supposed to contribute to a good breast shape in adulthood.

Blood from the nipples is nearly always benign and frequently associated with duct ectasia; it should only be investigated when it is unilateral.

Breast atrophy is the normal or spontaneous atrophy or shrinkage of the breasts.

Breast atrophy commonly occurs in women during menopause when estrogen levels decrease. It can also be caused by hypoestrogenism and/or hyperandrogenism in women in general, such as in antiestrogen treatment for breast cancer, in polycystic ovary syndrome (PCOS), and in malnutrition such as that associated with eating disorders like anorexia nervosa or with chronic disease. It can also be an effect of weight loss.

In the treatment of gynecomastia in males and macromastia in women, and in hormone replacement therapy (HRT) for trans men, breast atrophy may be a desired effect.

Examples of treatment options for breast atrophy, depending on the situation/when appropriate, can include estrogens, antiandrogens, and proper nutrition or weight gain.

This condition is also known as constricted breasts, tubular breasts, snoopy breasts (may be considered insulting), herniated areolar complexes, conical breast, domen nipple, lower pole hypoplasia and hypoplastic breasts.

Tuberous breasts are not simply small or underdeveloped breasts. The effect of the condition on the appearance of the breast can range from mild to severe, and typical characteristics include: enlarged, puffy areola, unusually wide spacing between the breasts, minimal breast tissue, sagging, higher than normal breast fold, and narrow base at the chest wall. The condition can cause low milk supply in breastfeeding women. However, other physical aspects of fertility and pregnancy are not affected by the condition.

The changes in fibrocystic breast disease are characterised by the appearance of fibrous tissue and a lumpy, cobblestone texture in the breasts. These lumps are smooth with defined edges, and are usually free-moving in regard to adjacent structures. The bumps can sometimes be obscured by irregularities in the breast that are associated with the condition. The lumps are most often found in the upper, outer sections of the breast (nearest to the armpit), but can be found throughout the breast. Women with fibrocystic changes may experience a persistent or intermittent breast aching or breast tenderness related to periodic swelling. Breasts and nipples may be tender or itchy.

Symptoms follow a periodic trend tied closely to the menstrual cycle. Symptoms tend to peak in the days and, in severe cases, weeks before each period and decrease afterwards. At peak, breasts may feel full, heavy, swollen, and tender to the touch. No complications related to breastfeeding have been found.

In ICD-10 the condition is called "diffuse cystic mastopathy", or, if there is epithelial proliferation, "fibrosclerosis of breast". Other names for this condition include "chronic cystic mastitis", "fibrocystic mastopathy" and "mammary dysplasia". The condition has also been named after several people (see eponyms below). Since it is a very common disorder, some authors have argued that it should not be termed a "disease", whereas others feel that it meets the criteria for a disease. It is not a classic form of mastitis (breast inflammation).

Galactorrhea can take place as a result of dysregulation of certain hormones. Hormonal causes most frequently associated with galactorrhea are hyperprolactinemia and thyroid conditions with elevated levels of thyroid-stimulating hormone (TSH) or thyrotropin-releasing hormone (TRH). No obvious cause is found in about 50% of cases.

Lactation requires the presence of prolactin, and the evaluation of galactorrhea includes eliciting a history for various medications or foods (methyldopa, opioids, antipsychotics, serotonin reuptake inhibitors, as well as licorice) and for behavioral causes (stress, and breast and chest wall stimulation), as well as evaluation for pregnancy, pituitary adenomas (with overproduction of prolactin or compression of the pituitary stalk), and hypothyroidism. Adenomas of the anterior pituitary are most often prolactinomas. Overproduction of prolactin leads to cessation of menstrual periods and infertility, which may be a diagnostic clue. Galactorrhea may also be caused by hormonal imbalances owing to birth control pills.

Galactorrhea is also a side effect associated with the use of the second-generation H receptor antagonist cimetidine (Tagamet). Galactorrhea can also be caused by antipsychotics that cause hyperprolactinemia by blocking dopamine receptors responsible for control of prolactin release. Of these, risperidone is the most notorious for causing this complication. Case reports suggest proton-pump inhibitors have been shown to cause galactorrhea.

An estrogen-dependent condition, disease, disorder, or syndrome, is a medical condition that is, in part or full, dependent on, or is sensitive to, the presence of estrogenic activity in the body.

Known estrogen-dependent conditions include mastodynia (breast pain/tenderness), breast fibroids, mammoplasia (breast enlargement), macromastia (breast hypertrophy), gynecomastia, breast cancer, precocious puberty in girls, melasma, menorrhagia, endometriosis, endometrial hyperplasia, adenomyosis, uterine fibroids, uterine cancers (e.g., endometrial cancer), ovarian cancer, and hyperestrogenism in males such as in certain conditions like cirrhosis and Klinefelter's syndrome.

Such conditions may be treated with drugs with antiestrogen actions, including selective estrogen receptor modulators (SERMs) such as tamoxifen and clomifene, estrogen receptor antagonists such as fulvestrant, aromatase inhibitors such as anastrozole and exemestane, gonadotropin-releasing hormone (GnRH) analogues such as leuprolide and cetrorelix, and/or other antigonadotropins such as danazol, gestrinone, megestrol acetate, and medroxyprogesterone acetate.

Galactorrhea (also spelled galactorrhoea) ( + ) or lactorrhea ( + ) is the spontaneous flow of milk from the breast, unassociated with childbirth or nursing.

Galactorrhea is reported to occur in 5–32% of women. Much of the difference in reported incidence can be attributed to different definitions of galactorrhea. Although frequently benign, it may be caused by serious underlying conditions and should be properly investigated. Galactorrhea also occurs in males, newborn infants and adolescents of both sexes.

Nipple discharge refers to any fluid that seeps out of the nipple of the breast. Discharge from the nipple does not occur in lactating women. And discharge in non-pregnant women or women who are not breasfeeding may not cause concern. Men that have discharge from their nipples are not typical. Discharge from the nipples of men or boys may indicate a problem. Discharge from the nipples can appear without squeezing or may only be noticeable if the nipples are squeezed. One nipple can have discharge while the other does not. The discharge can be clear, green, bloody, brown or straw-colored. The consistenct can be thick, thin, sticky or watery.

Some cases of nipple discharge will clear on their own without treatment. Nipple discharge is most often not cancer (benign), but rarely, it can be a sign of breast cancer. It is important to find out what is causing it and to get treatment. Here are some reasons for nipple discharge:

- Pregnancy

- Recent breastfeeding

- Rubbing on the area from a bra or t-shirt

- Trauma

- Infection

- Inflammation and clogging of the breast ducts

- Noncancerous pituitary tumors

- Small growth in the breast that is usually not cancer

- Severe underactive thyroid gland (hypothyroidism)

- Fibrocystic breast (normal lumpiness in the breast)

- Use of certain medicines

- Use of certain herbs, such as anise and fennel

- Widening of the milk ducts

- Intraductal pipilloma

- Subareolar abscess

- Mammary duct ectasia

- Pituitary tumor

Sometimes, babies can have nipple discharge. This is caused by hormones from the mother before birth. It usually goes away in 2 weeks. Cancers such as Paget disease (a rare type of cancer involving the skin of the nipple) can also cause nipple discharge.

Nipple discharge that is NOT normal is bloody, comes from only one nipple, or comes out on its own without squeezing or touching the nipple. Nipple discharge is more likely to be normal if it comes out of both nipples or happens when the nipple is squeezed. Squeezing the nipple to check for discharge can make it worse. Leaving the nipple alone may make the discharge stop.

Micromastia (also called hypomastia, breast aplasia, breast hypoplasia, or mammary hypoplasia) is a medical term describing the postpubertal underdevelopment of a woman's breast tissue. Just as it is impossible to define 'normal' breast size, there is no objective definition of micromastia. Breast development is commonly asymmetric and one or both breasts may be small. This condition may be a congenital defect associated with underlying abnormalities of the pectoral muscle (as in Poland's syndrome), related to trauma (typically surgery or radiotherapy) or it may be a more subjective aesthetic description.

Self perceived micromastia involves a discrepancy between a person's body image, and her internalized images of appropriate or desirable breast size and shape. Societal ideals over breast size vary over time, but there exist many conceived ideas involving breasts and sexual attractiveness and identity across different cultures.

Micromastia can be congenital or disorder and may be unilateral or bilateral. Congenital causes include ulnar–mammary syndrome (caused by mutations in the TBX3 gene), Poland syndrome, Turner syndrome, and congenital adrenal hyperplasia. There is also a case report of familial hypoplasia of the nipples and athelia associated with mammary hypoplasia that was described in a father and his daughters. Acquired causes of micromastia include irradiation in infancy and childhood and surgical removal of prepubertal breast bud.

Lactation mastitis usually affects only one breast and the symptoms can develop quickly. The signs and symptoms usually appear suddenly and they include:

- Breast tenderness or warmth to the touch

- General malaise or feeling ill

- Swelling of the breast

- Pain or a burning sensation continuously or while breast-feeding

- Skin redness, often in a wedge-shaped pattern

- Fever of 101 F (38.3 C) or greater

- The affected breast can then start to appear lumpy and red.

Some women may also experience flu-like symptoms such as:

- Aches

- Shivering and chills

- Feeling anxious or stressed

- Fatigue

Contact should be made with a health care provider with special breastfeeding competence as soon as the patient recognizes the combination of signs and symptoms. Most of the women first experience the flu-like symptoms and just after they may notice a sore red area on the breast. Also, women should seek medical care if they notice any abnormal discharge from the nipples, if breast pain is making it difficult to function each day, or they have prolonged, unexplained breast pain.

Breast diseases can be classified either with disorders of the integument, or disorders of the reproductive system. A majority of breast diseases are noncancerous.

Nipple discharge is the release of fluid from the nipples of the breasts. Abnormal nipple discharge may be described as any discharge not associated with lactation. The nature of the discharge may range in color, consistency and composition, and occur in one or both breasts. Although it is considered normal in a wide variety of circumstances it is the third major reason involving the breasts for which women seek medical attention, after breast lumps and breast pain. It is also known to occur in adolescent boys and girls going through puberty.

Breast tension is a constellation of symptoms involving the breasts including:

- Breast tenderness

- Breast pain

- Breast engorgement

Comedo mastitis is a very rare form similar to granulomatous mastitis but with tissue necrosis. Because it is so rare it may be sometimes confused with comedo carcinoma of the breast although the conditions appear to be completely unrelated.

Female breast ptosis or sagging is a natural consequence of aging. The rate at which a woman's breasts droop and the degree of ptosis depends on many factors. The key factors influencing breast ptosis over a woman's lifetime are cigarette smoking, her number of pregnancies, gravity, higher body mass index, larger bra cup size, and significant weight gain and loss. Post-menopausal women or people with collagen deficiencies (such as ehlers-danlos) may experience increased ptosis due to a loss of skin elasticity. Many women and medical professionals mistakenly believe that breastfeeding increases sagging. It is also commonly believed that the breast itself offers insufficient support and that wearing a bra prevents sagging which has not been found to be true.

Plastic surgeons categorize the severity of ptosis by evaluating the position of the nipple relative to the infra-mammary fold, the point at which the underside of the breasts attach to the chest wall. In the most advanced stage, the nipples are below the fold and point towards the ground.

A woman's breasts change in size, volume, and position on her chest throughout her life. In young women with large breasts, sagging may occur early in life due to the effects of gravity. It may be primarily caused by the volume and weight of the breasts which are disproportionate to her body size.